Chemistery P3 Merged

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the May/June 2010 question paper

for the guidance of teachers

0620 CHEMISTRY

0620/31 Paper 31 (Extended Theory), maximum raw mark 80

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers.

Mark schemes must be read in conjunction with the question papers and the report on the examination.

• CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2010 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

www.XtremePapers.com

Mark Scheme: Teachers’ version Syllabus Paper

IGCSE – May/June 2010 0620 31

© UCLES 2010

1 (i) sulfur [1] (ii) iodine [1] (iii) copper ignore (II) [1] (iv) calcium [1] (v) helium [1] not name of a compound accept correct symbols

2 (i) chloromethane [1] cond biggest molecular mass / biggest mass of one mole / its molecules move slowest / heaviest molecule / highest density [1] accept atomic mass if correct numerical value given ignore it is the heaviest (gas) / biggest molecule accept particles or molecules not atoms (ii) carbon dioxide / calcium carbonate [1] not methane water [1] sodium chloride / brine / seawater [1] (iii) chlorine [1] not chlorine water cond light / UV / heat / high temperature if numerical value given about 200oC / lead tetraethyl [1] not warm (iv) oxygen and nitrogen (in air) [1] not from fuel, negates mark 1 (react) at high temperatures / lightning / in engine [1] not combustion or exhaust, negates mark 2 (v) 2O3 � 3O2 [2] not balanced = [1] 3 (a) (i) bubbles / effervescence / hydrogen / gas pushes up / lifts metal [1] (ii) does not react with acid / zinc and iron react with acid [1] not just unreactive (b) (i) with copper / first experiment [1] (ii) copper acts as a catalyst [1]

(c) (i) smaller gradient [1] not rate is slower (ii) same final volume of hydrogen / same level (on graph) [1]



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(d) temperature / heat [1] increase temperature – reaction faster particles have more energy / particles move faster / particles collide more frequently / more particles have enough energy to react not more excited accept arguments for a decrease in temperature [1] powdered greater surface area greater collision rate / more particles exposed (to acid) any two [2] not concentration / light / catalyst / pressure 4 (a) (i) ethanol [1] CH3-CH2-OH [1] propanoic acid [1] CH3-CH2-COOH [1] independent marking, no ecf accept C2H5 not – HO (ii) type of compound – salt / sodium carboxylate / alkanoate [1] not soap / sodium stearate etc use – soap / cleaning / detergent [1] (iii) terylene / PET / Dacron / diolen / mylar / crimplene [1] (b) (i) polyamide / amide / peptide / polypeptide [1] (ii) correct amide linkage NHCO then CONH [1] cond to mark 1, 2 monomers (different shading in box) [1] cond continuation (to ONE correct linkage) [1] OR nylon 6 only one linkage – NHCO [1] cond only one monomer [1] cond continuation (to correct linkage) [1] (iii) use locating agent [1] measure distance travelled by sample / travelled by solvent front [1] cond this is Rf = 0.5 [1] for mark 3, either mark 1 or mark 2 must be awarded accept run a chromatogram of glycine [1] compare with sample same position [1] max [2]



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5 (a) (i) macromolecular / giant covalent / giant atomic [1] all atoms held in position / in tetrahedral structure / to four other carbon atoms / all strong bonds [1] (ii) jewellery / drilling / cutting / engraving / cutting edges in scalpels [1] mark first use offered (iii) layer structure / sheets [1] molecules / ions in layers = [0] layers can slide (over each other) [1] (iv) lubricant / pencils / electrodes [1] mark first use offered (b) (i) 4e between carbon and oxygens [1] 2 non-bonding pairs on both oxygens [1] cond correct coding – only scored if marks 1 and 2 awarded [1] ignore O2 in atom (ii) 4O around each Si [1] 2Si around each O [1] must refer to diagram not valencies or electron distributions (iii) SiO2 has higher mp or bp SiO2 is a solid, CO2 is a gas (at rtp) (when both are solids) then SiO2 is harder has higher density SiO2 insoluble, CO2 soluble [2] any two, comparison needed 6 (a) rates equal [1] concentrations do not change / macroscopic properties remain constant [1] accept amounts do not change (b) endothermic [1] cond favoured by high temperatures [1] (c) (i) move to left [1] cond bigger volume / more moles etc [1] do not insist on “gas” (ii) less yellow solid / more brown liquid [1] accept yellow to brown / less solid more liquid / goes brown



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7 (a) a transition element has more than one oxidation state or valency [1] accept different oxidation states (b) by removing oxygen concentration of O2 decreases [1] prevents the back reaction / equilibrium shifts to right [1] (c) oxidation number reduced (from (+) 4 to 0) [1] accept accepts electrons or accepts four electrons if number given must be 4 (d) low density / lightweight / light [1] propellers / fittings on ships / inert anodes in electrolysis / hip replacements / ship building / chemical plants / cathodic protection / diving equipment [1] (e) (i) percentage of oxygen = 31.6 % [1] (ii) calculate the number of moles of atoms for each element number of moles of Ti = 31.6/48 = 0.66 number of moles of O = 31.6/16 = 1.98 accept 2 [1] both correct for one mark (iii) the simplest whole number ratio for moles of atoms: Fe : Ti : O 1 1 3 [1] (iv) formula is FeTiO3 accept TiFeO3 [1] must be whole numbers from (iii) or cancelled numbers from (iii) mark ecf throughout



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8 (a) same general formula same chemical properties same functional group physical properties vary in predictable way common methods of preparation consecutive members differ by CH2 any two [2] mark first two ignore others unless it contradicts a point which has been awarded a mark (b) (i) 2HCOOH + CaCO3 � Ca(HCOO)2 + CO2 + H2O [2] not balanced = [1] (ii) zinc + methanoic acid � zinc methanoate + hydrogen [2] [1] for each product (iii) protected by oxide layer [1] (c) butanoic acid [1] CH3-CH2-CH2-COOH / C4H8O2 / C3H7COOH / C4H7OOH [1] C2H4O [1] mark ecf to molecular formula





0620 CHEMISTRY








© UCLES 2010

1 In (a), (b) and (c), descriptions of chemical properties need not be detailed. If more than one answer is given in each section, mark the first one and ignore anything subsequent unless it contradicts what they have already written. No marks for reversing physical and chemical properties.

(a) properties should focus on a group 1 metal and not just metals in general

PHYSICAL soft / can be cut (with a knife) / low density / light / low melting point / (good) conductor (heat or electricity) / shiny (when freshly cut) / malleable / ductile / tarnishes [1]

CHEMICAL react with water (not steam) / (very) reactive / forms salts with halogens / react vigorously with acids (ignore concentration) / forms an alkaline or basic oxide / fixed oxidation state or oxidation number or valency of +1 / has one valency or outer shell electron

not forms ionic compounds on its own. [1]

(b) properties should focus on a transition metal

PHYSICAL hard / high density / dense / high mp or bp / (good) conductor (heat or electricity) / strong / malleable / ductile / silver or grey or lustrous or shiny solid [1]

CHEMICAL more than one oxidation state or valency (accept many oxides) / forms coloured compounds or ions (not coloured on its own) / forms complex ions / behave as a catalyst

/ less reactive than group 1 [1]

(c) PHYSICAL colourless gas / yellow gas [1] not diatomic molecules CHEMICAL most reactive halogen / very reactive / forms ionic fluorides / bonds with metals /

form covalent fluorides / bonds with non-metals / powerful oxidant / gains one electron (to be stable) / fixed oxidation state or valency of –1

allow decolourised when reacts with alkene) / forms F– ions / forms acidic oxides / forms an acid when reacted with hydrogen / hydride is acidic [1]

not bleaching agent

2 (a) (i) enzymes are proteins / come from living organisms / biological (catalysts) [1] not enzymes are living or natural

(ii) carbohydrates have 2H:1O ratio [1] contain elements of water [1]

contain water = [1] unless they state that carbohydrates contain water, this response scores 2 or 0

(b) correct -O- linkage [1] cond same correct monomer (this mark is lost if 2 different boxes are shown) [1] cond continuation (i.e. bonds at both ends) [1]

(c) (i) (concentration or amount or mass etc.) of starch decreases (with time) [1] (concentration etc.) of starch becomes zero / all starch gone [1] colour (intensity) indicates how much starch is present (can be inferred) [1] (ii) enzyme denatured / destroyed [1] not enzymes killed / don’t work / saliva denatured



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3 (a) (i) red brown or orange to colourless [1] not just bromine decolourised yellow (not dark) / white solid / precipitate / goes cloudy [1] brown to yellow with no mention of solid/precipitate scores = [1] (ii) Br2 + Na2S � 2NaBr + S [1] (iii) look for two comments sulfide (ion) / sulfur (ion) loses electrons [1] not sodium sulfide bromine accepts them [1] (b) (i) oxidation [1] not redox (ii) hydrogen / H2 not H [1] (iii) iron(II) hydroxide / ferrous hydroxide [1] (iv) 4Fe(OH)2 + O2 + 2H2O � 4Fe(OH)3 [1] (v) oxidation number or state or valency increases / electron loss / Fe2+ to Fe3+ [1] not gains oxygen (vi) sacrificial protection or zinc is sacrificed / zinc corrodes not iron or zinc corrodes therefore iron doesn’t / not just zinc rusts zinc is oxidised in preference to iron / zinc reacts with oxygen and water in preference to iron / zinc more reactive or electropositive than iron / zinc forms ions more readily than iron or zinc loses electrons more readily than iron / electrons move on to iron / iron is cathode or zinc is anode / any three [3]



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4 (a) (i) same molecular formula / same number of C and H atoms [1] different structural formula or structure [1] same compound = [1]

(ii) correct formula of but-2-ene / methylpropene / methyl cyclopropane [1]

(iii) bromine / bromine water / aqueous bromine [1] brown to colourless not clear [1] stays brown [1] bromide loses the first mark only

OR alkaline potassium manganate(VII) [1] from purple/pink to green/brown [1] stays purple [1]

OR acidic potassium manganate(VII) [1] from purple/pink to colourless not clear [1] stays purple [1]

(b) heat / high temperature (temperature need not be stated, but if it is stated it must be 500ºC or above) [1]

catalyst (need not be named, but if they are named accept any metal oxide or zeolite / aluminosillicates / silicon dioxide) [1] not nickel/platinum

(c) (1,2)dibromobutane [1] if numbers given must be correct butane [1] butanol [1] accept butan-1-ol or butan-2-ol not but-1-ol / but-1-anol / buthanol

5 (a) fractional [1] distillation [1]

(b) (i) O=O / oxygen(–)oxygen / H–H / hydrogen(–)hydrogen [1] (ii) O-H / oxygen(–)hydrogen / OH / bond between hydrogen and oxygen [1] not H-O-H (iii) endothermic. [1]

(c) (i) no pollution / no CO / no CO2 / no oxides of nitrogen / only produces steam or water / no greenhouse gases / no global warming [1] does not use up fossil fuels / water is not a finite resource / water is a renewable source of energy / hydrogen is renewable / available from electrolysis of water [1]

(ii) obtaining hydrogen from water requires fossil fuels / storage problems / transport problems / limited range of vehicles available / gaseous nature means only produces small amount of energy per unit volume / methane as a source of steam reforming is finite / lack of distribution network [1]

not expensive / anything regarding safety / flammability / explosiveness



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6 (a) (i) Tl 2S [1]

(ii) TlCl

3 [1] (b) filter / centrifuge / decant wash the precipitate dry the solid / heat the solid (in oven) / press between filter paper [3] all three stated but not in correct order = [2] two out of three stated in any order = [1] (c) (i) silver chloride / silver bromide [1] photography / cameras / films / photo chromic lenses / sunglasses [1] (ii) increase distance between lamp and paper or put lamp far away / put a screen or translucent or semi-opaque material between them / use a less powerful or low voltage or dim lamp / lower the temperature any two [2] (d) (i) thalium sulfate + ammonia + water [1] (ii) 2TlOH + H2SO4 � Tl2SO4 + 2H2O [2] not balanced = [1] incorrect formula = [0] (iii) green precipitate or solid (ignore shades of green but not bluey green etc.) [1] Fe2+ + 2OH– � Fe(OH)2 accept multiples [1] 7 (a) sodium is expensive / difficult to obtain sodium (from sodium chloride) / problems getting

electricity / hard to extract sodium / high energy costs in extraction of sodium [1] (b) (i) reduce temperature / reduce melting point (to 900/1000°C) temperature need not be

stated, but if it is stated it must be within the range better conductivity / solid aluminium oxide does not conduct aluminium oxide is insoluble in water any two [2] (ii) 2O2– � O2 + 4e– [2] or [0] (iii) they burn (away) / react with oxygen / form carbon dioxide [1] (c) hydrogen formed / aluminium above hydrogen in reactivity series / H+ discharged in preference to Al3+ / aluminium is more reactive than hydrogen [1] aluminium more reactive than carbon / carbon cannot reduce aluminium oxide /

aluminium is higher than carbon in the reactivity series / carbon doesn’t reduce aluminium oxide / carbon doesn’t displace aluminium [1]

comparison is essential for mark



© UCLES 2010

8 (a) (i) accept all metals excluding Group I (lithium is acceptable) [1] not lead accept silver (ii) M nitrite / nitrate(III) [1] not nitride (b) (i) exothermic [1] not reverse reaction is endothermic as the question asks about the forward reaction cond forward reaction favoured by low temperature / reverse reaction favoured by high temperature [1] second mark only scores if exothermic is correct. (ii) position of equilibrium to right / forwards / more products / more N2O4 / lighter colour [1] because this side has smaller volume / fewer moles [1] (c) if the final answer is between 86–89% award all 4 if the final answer is between 66–67% award 3 marks (Mr of 32 must have been used) for all other answers marks can be awarded using the mark scheme as below and applying

ecf if necessary number of moles of O2 formed = 0.16/24 = 0.0067/0.00667 or 1/150 number of moles of Pb(NO3)2 in the sample = 0.0133/0.013 or 1/75 mass of one mole of Pb(NO3)2 = 331 g mass of lead(II) nitrate in the sample = 4.4(1) g percentage of lead(II) nitrate in sample = 88.3% (allow 88–89) [4] mark ecf in this question but not to simple integers if mass of lead(II) nitrate > 5.00 only marks 1 and 2 available If divides by 32 (not 24) only last 3 marks can score consequentially





0620 CHEMISTRY








© UCLES 2010

1 In (a), (b) and (c), descriptions of chemical properties need not be detailed. If more than one answer is given in each section, mark the first one and ignore anything subsequent unless it contradicts what they have already written. No marks for reversing physical and chemical properties.

(a) properties should focus on a group 1 metal and not just metals in general

PHYSICAL soft / can be cut (with a knife) / low density / light / low melting point / (good) conductor (heat or electricity) / shiny (when freshly cut) / malleable / ductile / tarnishes [1]

CHEMICAL react with water (not steam) / (very) reactive / forms salts with halogens / react vigorously with acids (ignore concentration) / forms an alkaline or basic oxide / fixed oxidation state or oxidation number or valency of +1 / has one valency or outer shell electron

not forms ionic compounds on its own. [1]

(b) properties should focus on a transition metal

PHYSICAL hard / high density / dense / high mp or bp / (good) conductor (heat or electricity) / strong / malleable / ductile / silver or grey or lustrous or shiny solid [1]

CHEMICAL more than one oxidation state or valency (accept many oxides) / forms coloured compounds or ions (not coloured on its own) / forms complex ions / behave as a catalyst

/ less reactive than group 1 [1]

(c) PHYSICAL colourless gas / yellow gas [1] not diatomic molecules CHEMICAL most reactive halogen / very reactive / forms ionic fluorides / bonds with metals /

form covalent fluorides / bonds with non-metals / powerful oxidant / gains one electron (to be stable) / fixed oxidation state or valency of –1

allow decolourised when reacts with alkene) / forms F– ions / forms acidic oxides / forms an acid when reacted with hydrogen / hydride is acidic [1]

not bleaching agent

2 (a) (i) enzymes are proteins / come from living organisms / biological (catalysts) [1] not enzymes are living or natural

(ii) carbohydrates have 2H:1O ratio [1] contain elements of water [1]

contain water = [1] unless they state that carbohydrates contain water, this response scores 2 or 0

(b) correct -O- linkage [1] cond same correct monomer (this mark is lost if 2 different boxes are shown) [1] cond continuation (i.e. bonds at both ends) [1]

(c) (i) (concentration or amount or mass etc.) of starch decreases (with time) [1] (concentration etc.) of starch becomes zero / all starch gone [1] colour (intensity) indicates how much starch is present (can be inferred) [1] (ii) enzyme denatured / destroyed [1] not enzymes killed / don’t work / saliva denatured



© UCLES 2010

3 (a) (i) red brown or orange to colourless [1] not just bromine decolourised yellow (not dark) / white solid / precipitate / goes cloudy [1] brown to yellow with no mention of solid/precipitate scores = [1] (ii) Br2 + Na2S � 2NaBr + S [1] (iii) look for two comments sulfide (ion) / sulfur (ion) loses electrons [1] not sodium sulfide bromine accepts them [1] (b) (i) oxidation [1] not redox (ii) hydrogen / H2 not H [1] (iii) iron(II) hydroxide / ferrous hydroxide [1] (iv) 4Fe(OH)2 + O2 + 2H2O � 4Fe(OH)3 [1] (v) oxidation number or state or valency increases / electron loss / Fe2+ to Fe3+ [1] not gains oxygen (vi) sacrificial protection or zinc is sacrificed / zinc corrodes not iron or zinc corrodes therefore iron doesn’t / not just zinc rusts zinc is oxidised in preference to iron / zinc reacts with oxygen and water in preference to iron / zinc more reactive or electropositive than iron / zinc forms ions more readily than iron or zinc loses electrons more readily than iron / electrons move on to iron / iron is cathode or zinc is anode / any three [3]



© UCLES 2010

4 (a) (i) same molecular formula / same number of C and H atoms [1] different structural formula or structure [1] same compound = [1]

(ii) correct formula of but-2-ene / methylpropene / methyl cyclopropane [1]

(iii) bromine / bromine water / aqueous bromine [1] brown to colourless not clear [1] stays brown [1] bromide loses the first mark only

OR alkaline potassium manganate(VII) [1] from purple/pink to green/brown [1] stays purple [1]

OR acidic potassium manganate(VII) [1] from purple/pink to colourless not clear [1] stays purple [1]

(b) heat / high temperature (temperature need not be stated, but if it is stated it must be 500ºC or above) [1]

catalyst (need not be named, but if they are named accept any metal oxide or zeolite / aluminosillicates / silicon dioxide) [1] not nickel/platinum

(c) (1,2)dibromobutane [1] if numbers given must be correct butane [1] butanol [1] accept butan-1-ol or butan-2-ol not but-1-ol / but-1-anol / buthanol

5 (a) fractional [1] distillation [1]

(b) (i) O=O / oxygen(–)oxygen / H–H / hydrogen(–)hydrogen [1] (ii) O-H / oxygen(–)hydrogen / OH / bond between hydrogen and oxygen [1] not H-O-H (iii) endothermic. [1]

(c) (i) no pollution / no CO / no CO2 / no oxides of nitrogen / only produces steam or water / no greenhouse gases / no global warming [1] does not use up fossil fuels / water is not a finite resource / water is a renewable source of energy / hydrogen is renewable / available from electrolysis of water [1]

(ii) obtaining hydrogen from water requires fossil fuels / storage problems / transport problems / limited range of vehicles available / gaseous nature means only produces small amount of energy per unit volume / methane as a source of steam reforming is finite / lack of distribution network [1]

not expensive / anything regarding safety / flammability / explosiveness



© UCLES 2010

6 (a) (i) Tl 2S [1]

(ii) TlCl

3 [1] (b) filter / centrifuge / decant wash the precipitate dry the solid / heat the solid (in oven) / press between filter paper [3] all three stated but not in correct order = [2] two out of three stated in any order = [1] (c) (i) silver chloride / silver bromide [1] photography / cameras / films / photo chromic lenses / sunglasses [1] (ii) increase distance between lamp and paper or put lamp far away / put a screen or translucent or semi-opaque material between them / use a less powerful or low voltage or dim lamp / lower the temperature any two [2] (d) (i) thalium sulfate + ammonia + water [1] (ii) 2TlOH + H2SO4 � Tl2SO4 + 2H2O [2] not balanced = [1] incorrect formula = [0] (iii) green precipitate or solid (ignore shades of green but not bluey green etc.) [1] Fe2+ + 2OH– � Fe(OH)2 accept multiples [1] 7 (a) sodium is expensive / difficult to obtain sodium (from sodium chloride) / problems getting

electricity / hard to extract sodium / high energy costs in extraction of sodium [1] (b) (i) reduce temperature / reduce melting point (to 900/1000°C) temperature need not be

stated, but if it is stated it must be within the range better conductivity / solid aluminium oxide does not conduct aluminium oxide is insoluble in water any two [2] (ii) 2O2– � O2 + 4e– [2] or [0] (iii) they burn (away) / react with oxygen / form carbon dioxide [1] (c) hydrogen formed / aluminium above hydrogen in reactivity series / H+ discharged in preference to Al3+ / aluminium is more reactive than hydrogen [1] aluminium more reactive than carbon / carbon cannot reduce aluminium oxide /

aluminium is higher than carbon in the reactivity series / carbon doesn’t reduce aluminium oxide / carbon doesn’t displace aluminium [1]

comparison is essential for mark



© UCLES 2010

8 (a) (i) accept all metals excluding Group I (lithium is acceptable) [1] not lead accept silver (ii) M nitrite / nitrate(III) [1] not nitride (b) (i) exothermic [1] not reverse reaction is endothermic as the question asks about the forward reaction cond forward reaction favoured by low temperature / reverse reaction favoured by high temperature [1] second mark only scores if exothermic is correct. (ii) position of equilibrium to right / forwards / more products / more N2O4 / lighter colour [1] because this side has smaller volume / fewer moles [1] (c) if the final answer is between 86–89% award all 4 if the final answer is between 66–67% award 3 marks (Mr of 32 must have been used) for all other answers marks can be awarded using the mark scheme as below and applying

ecf if necessary number of moles of O2 formed = 0.16/24 = 0.0067/0.00667 or 1/150 number of moles of Pb(NO3)2 in the sample = 0.0133/0.013 or 1/75 mass of one mole of Pb(NO3)2 = 331 g mass of lead(II) nitrate in the sample = 4.4(1) g percentage of lead(II) nitrate in sample = 88.3% (allow 88–89) [4] mark ecf in this question but not to simple integers if mass of lead(II) nitrate > 5.00 only marks 1 and 2 available If divides by 32 (not 24) only last 3 marks can score consequentially



MARK SCHEME for the October/November 2010 question paper


0620 CHEMISTRY




• CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2010 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.



IGCSE – October/November 2010 0620 31

© UCLES 2010

1 (a) (i) same number of protons and electrons [1] (ii) all have the same number of protons / same proton number / same atomic number [1] (iii) more electrons than protons [2] number of protons and electrons not equal ONLY [1] (iv) same number of protons (and electrons) / same proton number / same atomic number [1] different number of neutrons / different mass number / nucleon number [1] (b) (i) 2 + 8 + 5 [1] (ii) 3 / 5 [1] (iii) non-metal because it accepts electrons / needs 3e to complete outer energy level / because it is in Group V or 5e in outer shell [1] note need both non-metal and reason for [1] [Total: 9] 2 (a) (i) harder / stronger / any sensible suggestion which relates to better properties for purpose e.g. stays sharp longer / cuts better / more corrosion resistant [1] (ii) zinc [1] (b) (i) lattice [1] (ii) regular pattern of one type of atom [1] with different atom interspersed [1] can show the difference – size, shading, label etc. (iii) can change its shape by force / plastically deform / can be hammered into sheets / can

bend etc. [1] (iv) particles / ions / atoms / layers [1] cond can slide past each other [1] or metallic bond is non-directional [1] particles can move past each other [1]



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(c) (i) tin(IV) oxide + carbon → tin + carbon dioxide [1] not carbon monoxide as a reductant accept carbon monoxide as a product not tin(IV) accept correct symbol equation (ii) water [1] carbon dioxide [1] (iii) correct labels for (pure) copper cathode [1] impure copper anode [1] electrolyte copper(II) sulfate / any soluble copper(II) salt / Cu2+ [1] if labels on electrodes reversed [0] (iv) wires / pipes / jewellery / nails / roofing / ammunition / coins / cookware / catalyst /

sculpture [1] [Total: 15] 3 (i) chemical [1] (ii) from right to left [1] not through salt bridge

(iii) Br2 + 2e → 2Br- [2] for Br- as product [1] (iv) reduction because electron gain [1] / because oxidation number decreases need both points (v) Fe3+ [1] (vi) any correct discussion of the reactivity of the halogens [1] e.g. the more reactive the halogen the higher the voltage not better conductor [Total: 7]



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4 (a) (i) nitrogen 2+5 [1] (ii) needs three electrons [1] to complete energy level [1] (b) (i) expensive metal / iron cheaper / better catalyst [1] (ii) high pressure favours side with smaller volume / fewer moles [1] this is right hand side / product / ammonia side [1] (iii) recycled / sent over catalyst again [1] accept used again (iv) advantage high yield [1] disadvantage slow reaction rate etc [1] [Total: 9] 5 (a) (i) many (simple) molecules form one (large) molecule / monomer molecules form one

polymer molecule [1] (ii) addition - polymer is the only product [1] accept - nX � Xn condensation polymer and simpler molecules formed [1] accept nX � Xn + nHCl / H2O

(b) (i) C12H26 → C8H18 + 2C2H4 [1] / any other correct version (ii) ethane and chlorine give range of products [1] / ethene more readily available than ethane / waste half chlorine as hydrogen chloride / ethene more reactive than ethane (iii) electrolysis [1] aqueous sodium chloride [1] (iv) must have three correct units [1] cond continuation [1] accept –(CH2–CH(Cl))n– [Total: 9]



© UCLES 2010

6 (a) (i) does not form compounds / does not accept and does not lose electrons / has full outer shell/has 8e in outer shell / it is a Noble Gas / it is in Group 0/8 [1]

(ii) small number of outer electrons / lose electrons then positive [1] large number of outer electrons / gain electrons then negative [1] (iii) any two from nitrogen, oxygen and fluorine [1] accept symbols / molecular formulae (b) (i) zinc / aluminium / lead / tin / chromium [1] (ii) white precipitate [1] precipitate dissolves / colourless solution forms / forms a clear solution / soluble in excess [1] (c) (i) LiF [1] NF3 [1] (ii) LiF has higher mp / bp LiF is a (crystalline) solid, NF3 is probably a gas / a liquid / LiF is less volatile as liquids only LiF conducts LiF is soluble in water, NF3 is not when both solids LiF is harder any two [2] (iii) LiF is an ionic compound [1] NF3 is a covalent/molecular compound [1] for stating that one is ionic and the other covalent [1] without specifying which is which [Total: 13] 7 (i) methane / water vapour / oxides of nitrogen / hydrofluorocarbons / perfluorocarbons /

ozone [1] not sulfur dioxide (ii) living organisms / plants and animals / cells [1] produce energy (from food / glucose / carbohydrates) [1] this forms carbon dioxide (could be in an equation) [1] (iii) when growing the crop removed carbon dioxide from atmosphere [1] / crop photosynthesised and used carbon dioxide combustion returned the carbon dioxide [1] (iv) increased combustion [1] of fossil fuels / named fossil fuel [1] or deforestation [1] less photosynthesis [1] not greater population

[Total: 8]



© UCLES 2010

8 (a) filter / centrifuge / decant [1] (partially) evaporate / heat / boil [1] allow to crystallise / cool / let crystals form [1] dry crystals / dry between filter paper / leave in a warm place to dry [1] “dry” on its own must be a verb evaporate to dryness only marks 1 and 2 note if discuss residue only mark 1 (b) number of moles of HCl used = 0.04 × 2 = 0.08

number of moles CoCl2 formed = 0.04 number of moles CoCl2.6H2O formed = 0.04 mass of one mole of CoCl2.6H2O = 238 g maximum yield of CoCl2.6H2O = 9.52g [4] accept 9.5 g mark ecf to moles of HCl do not mark ecf to integers to show that cobalt(II) carbonate is in excess number of moles of HCl used = 0.08 must use value above ecf mass of one mole of CoCO3 = 119g number of moles of CoCO3 in 6.0g of cobalt(II) carbonate = 6.0/119 = 0.050 [1] reason why cobalt(II) carbonate is in excess 0.05 > 0.08/2 [1] [Total: 10]





0620 CHEMISTRY








© UCLES 2010

1 (a) E [1] (b) A C E need all three [1] (c) A [1] (d) F [1] (e) C [1] (f) D F need both but not more [1]

[Total: 6] 2 (a) (i) heat / roast / combustion / high temperature [1] accept burn in air / oxygen [1] any incorrect Chemistry MAX [1] (ii) ZnO + C → Zn + CO [1] OR 2ZnO + C → 2Zn + CO2 the equation must balance, if not [0] not carbon monoxide as a reactant / (iii) fractional [1] distillation [1] (b) (i) making alloys / brass / named alloy which contains zinc [1] galvanising / sacrificial protection / electroplating [1] accept galvanising / one specific use which depends on galvanising zinc coated screws / roofing / buckets / sinks not just plating other metals (ii) positive ions / cations [1] not nuclei / atoms delocalised / free / mobile or sea of electrons [1] bond is attraction between (positive) ions and delocalised electrons [1] it is a good conductor because there are delocalised / free / mobile electrons [1] Note must be clear that electrons are moving / carry charge / reason why it is a good conductor

[Total: 11]



© UCLES 2010

3 (a) volume given off (in that 20 s interval) [1] divided by 20 [1] accept 48/20 for [2] Answer to 3 (a) may appear twice, both in 3 (a) and 3 (b). Please ignore in 3 (b). (b) 0.6 (cm3/s) [1] (c) concentration [1] of hydrogen peroxide decreases [1]

for hydrogen peroxide used up ONLY [1] not reagent / reactant (d) rate increases / doubles [1] catalyst has bigger surface area / more catalyst particles exposed [1] more collisions [1] not more catalyst / higher concentration of catalyst / more molecules of catalyst

OR

volume of oxygen the same [1] oxygen from hydrogen peroxide (not catalyst) [1] amount / number of moles the same [1]

OR

amount/mass/volume/number of moles of hydrogen peroxide the same [2]

catalyst chemically unchanged ONLY [1] reactants have not changed (only the catalyst) [1] accept catalyst does not react [1]

[Total: 11]

4 (a) (i) chromium is harder has higher density has higher melting point / boiling point / fixed points stronger any TWO [2] accept sodium comments must be comparison chromium is hard [0]

(ii) both chromium and sodium have to be mentioned explicitly or implicitly. sodium is more reactive is acceptable sodium is a reactive metal is not acceptable chromium has more than one oxidation state, sodium has one chromium forms coloured compounds, sodium compounds are white / sodium does not sodium reacts with cold water, chromium does not chromium forms complex ions, sodium does not accept chromium has catalytic properties, sodium does not any TWO [2]



© UCLES 2010

(b) (i) appearance/shiny/more attractive/decoration resist corrosion / rusting hard surface any TWO [2] NOT becomes harder / stronger (ii) Cr2(SO4)3 [1] ignore correct charges on ions (iii) Cr3+ + 3e → Cr [2] Cr3+ to Cr only [1] ignore comments about sulfate ion (iv) oxygen / O2 [1] (v) to replace chromium ions (used to plate steel) [1] / chromium sulfate used up copper ions replaced from copper anode [1] / solution of copper sulfate does not change not just that anode is not made of chromium

[Total: 12] 5 (a) (i) contains carbon, hydrogen and oxygen [1] accept example ratio 2H : 1O [1] not contains water ignore comments about carbon (ii) living organism / plants and animals / cells [1] obtain energy from food [1] not burn negates energy mark (iii) carbohydrates contain oxygen [1] (iv) as a fertiliser / manure [1] (b) (i) 80 cm3 of oxygen therefore 40 cm3 of methane [1] 40/60 × 100 = 66.7 % [1] accept 66 % and 67 % no ecf (ii) add sodium hydroxide(aq) / alkali [1] carbon dioxide dissolves, leaving methane [1]

[Total: 10]



© UCLES 2010

6 (a) same general formula consecutive members differ by CH2 same chemical properties same functional group physical properties vary in predictable way / give trend – mp increases with n etc. common methods of preparation any THREE [3] (b) (i) they have the same molecular formula [1] not general formula different structures / structural formulae [1] (ii) CH3-CH2-CH(OH)-CH3 / (CH3)3C-OH [1] not ether-type structures NOTE butan-2-ol and 2-methylpropan-2-ol acceptable (c) (i) air/oxygen / (acidified) potassium chromate(VI) / (acidified) potassium manganate(VII) [1] must have oxidation states (ii) carboxylic acid / alkanoic acid [1] CH3-CH2-CH2-COOH / C3H7COOH / C4H8O2 [1] accept C4H7OOH (d) (i) measure volume of carbon dioxide [1] time [1] accept day / hour for time mark (ii) increase in temperature / more yeast present / yeast multiplies [1] (iii) glucose used up [1] accept sugar not reagent / reactant concentration of ethanol high enough to kill/poison yeast / denature enzymes [1] not kill enzymes (iv) to prevent aerobic respiration [1] / ethanol would be oxidised / ethanoic acid/ acid formed / lactic acid formed / carbon

dioxide and water formed

[Total: 15]



© UCLES 2010

7 (a) (i) kills microbes / bacteria / fungi / micro-organisms etc. [1] (ii) as a bleach [1] (iii) burn / heat sulfur in air / oxygen [1] (b) oxygen [1] vanadium oxide / vanadium(V) oxide / vanadium pentoxide [1] not an incorrect oxidation state 400 °C to 450 °C [1] water [1] (c) (i) proton donor [1] (ii) measure pH / use pH paper [1] sulfuric acid has the lower pH [1] accept colours / appropriate numerical values OR measure electrical conductivity [1] sulfuric acid is the better conductor [1] OR add magnesium / named fairly reactive metal [1] ethanedioic acid gives the slower reaction [1] NOTE result must refer to rate not amount OR add a carbonate [1] ethanedioic acid gives the slower reaction [1] NOTE result must refer to rate not amount (d) (i) how many moles of H2SO4 were added = 0.02 × 0.3 = 0.006 [1] (ii) how many moles of NaOH were used = 0.04 × 0.2 = 0.008 [1] (iii) sulfuric acid [1] only mark ecf if in accord with 1:2 ratio and with values from (i) and (ii). reason 0.006 > 0.008/2 [1] for ecf mark candidate must use 1:2 ratio in answer (iv) less than 7 [1]

[Total: 15]





0620 CHEMISTRY








© UCLES 2010

1 (a) to complete the outer shell (of oxygen) / full outer or valence shell / 8 (electrons) in outer shell / Noble gas structure / to complete outer shell / to complete the octet

ignore reference to hydrogen atoms / reference to accepting / sharing or gaining electrons [1] (b) loses (one) electron [1] not loses electrons (c) opposite charges attract / electrostatic attraction / positive attracts negative / + and – attract

[1] (d) in solid ions cannot move / flow / no free ions / ions in a lattice [1] in solution ions can move / flow / mobile ions / ions free (to move) [1]

[Total: 5] 2 (a) 23p 23e 28n [1] 23p 20e 28n [1] 23p 23e 27n [1] (b) (i) (contains) iron [1] cond with other element(s) / compounds / suitable named element [1] if iron is absent = 0 (ii) mild steel [1] cars / fridges / white goods / construction etc. [1] credit any sensible suggestion e.g. roofing, nails, screws, radiators or stainless steel [1] cutlery / chemical plant / jewellery / (kitchen) utensils / named kitchen utensil / in cars /

surgical equipment / car exhausts etc. [1] not vanadium steel (this is in the question) (c) (i) V2O3 [1] VO2 [1] (ii) add sodium hydroxide(aq) or other named alkali [1] not ammonia cond vanadium(IV) oxide dissolves / reacts [1] filter (to remove vanadium(III) oxide) [1]

[Total: 12]



© UCLES 2010

3 (a) (i) silver, tin (cobalt and magnesium not possible to decide) [2] for silver less reactive then tin = 1 (ii) magnesium and cobalt salt / compound / ions or cobalt and magnesium salt / compound / ions [1] (iii) Sn + 2Ag+ � Sn2+ + 2Ag [2] all species correct = 1 balancing = 1 Sn to Sn2+ oxidation (can be written separately or as a correct half-equation) [1] (b) no reaction [1] Mg(OH)2 � MgO + H2O accept multiples [1] (c) (i) it forms positive ions / loses or gives electrons [1] electrons move / flow from this electrode / enter the circuit / electrons flow from negative to positive (so it is negative) [1] (ii) bigger voltage of Zn/Cu cell than Sn/Cu cell or zinc is negative relative to tin (in the third cell) [1] (iii) magnesium / more reactive metal (must be named) instead of zinc not anything above calcium in the reactivity series or silver / less reactive metal (must be named) instead of copper or use (more) concentrated acid [1] (iv) polarities correct that is Zn - and Sn + [1] 0.6 V [1]

[Total: 14] 4 (a) (i) H2 on RHS [1] ignore any other species on RHS rest of equation fully correct i.e. 2H+ + 2e � H2 [1] (ii) H+ removed / escapes / discharged / used up / reduced [1] (equilibrium) moves to RHS / more water molecules ionise or dissociate / forward reaction favoured [1] (iii) oxygen / O2 [1] not O (iv) carbon / graphite / platinum (electrode) [1] (b) (i) to make ammonia / in petroleum processing / balloons / rocket fuel / fuel for cars /

hardening of fats / fuel cells / fuel (unqualified) / making hydrochloric acid [1] (ii) to sterilise / disinfect it / kill bacteria / bugs / microbes / micro-organisms / germs [1]



© UCLES 2010

(c) (i) (reference to) volume and time / how long it takes [1] (ii) carry out experiment with different intensities of light / one in light and one in dark / repeat experiment in reduced light [1] measure new rate which would be faster or slower depending on light intensity [1]

[Total: 11] 5 (a) (i) Mg + 2CH3COOH � (CH3COO)2Mg + H2 [1] correct formula of magnesium ethanoate [1] ignore charges sodium ethanoate + water [1] (ii) ethyl ethanoate [1] displayed formula [1] (b) (i) add up to 5.8 g [1] (ii) moles of C atoms = 2.4/12 = 0.2 moles of H atoms = 0.2/1 = 0.2 moles of O atoms = 3.2/16 = 0.2 all three correct = 2 [2] two correct = 1 empirical formula CHO [1] (iii) 116/29 = 4 [1] C4H4O4 [1] correct formula with no working scores both marks. (iv) HOOCCH=CHCOOH / CH2=C(COOH)2 [2]

[Total: 13] 6 (a) (i) 6e between two nitrogen atoms (can be any combination of dots or crosses) [1] 1 lone pair on each nitrogen atom [1] (ii) SOLID GAS PATTERN regular / lattice (not fixed) random / irregular / no pattern [1] DISTANCE close far apart / spread out [1] MOVEMENT vibrate / fixed / no motion moving / translational [1] (b) (i) particles/molecules have more energy / move faster [1] collide harder / collide more frequently / more collisions / collide with more force (with the

walls) [1]



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(ii) (1) nitrogen has smaller Mr / lighter molecules / lower density [1] nitrogen molecules / particles move faster (than chlorine molecules) [1] (2) at higher temperature nitrogen molecules or particles (not atoms) move faster /

have more energy [1]

[Total: 10] 7 (a) (i) lighter / light / lightweight / lower density [1] does not corrode / rust / oxidised [1] ignore cheaper / easier to mould (ii) credit any two sensible suggestions e.g. rope / clothing / netting / string / carpets / fishing

line / fishing nets / parachutes / tyres / tents / bottles / thread / umbrellas / curtains / toothbrushes / cassettes / video tapes [2]

(iii) non-biodegradeable / do not rot / do not decompose / persist for years / accumulate landfill sites limited / getting filled up visual pollution danger to fish / animals (burn to form) toxic gases / harmful gases / pollutant gases / acidic gases / CO / HCl /

HF / HCN not oxides of nitrogen / sulfur any three [3] (b) (i) propene / propylene [1] accept prop-1-ene not prop-2-ene CH3-CH=CH2 [1] double bond must be shown (ii) correct repeat unit (one or more whole repeat units must be given) [1] cond continuation [1] (c) (i) amide / peptide / polypeptide [1] (ii) protein / polypeptide [1] (iii) H2N(CH2)6NH2 [1] HOOC(CH2)8COOH

[Total: 15]





0620 CHEMISTRY




• Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May/June 2011 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.




© University of Cambridge International Examinations 2011

1 (a) F or B diffusion / fractional distillation [1] (b) A simple distillation [1] (c) D chromatography [1] (d) E filtration [1] (e) C evaporation [1] (f) B fractional distillation [1] 2 (a) (i) photosynthesis or a photochemical reaction [1] not an example, question requires a process not devices which convert light into electricity (ii) cell [1] accept battery not generator (b) (i) correct formula [1]

cond following marks conditional on correct formula If covalent mark 1 only correct charges [1] 6x and 2o around anion [1] do NOT penalise for incorrect coding ignore electrons around potassium

(ii) correct formula [1]

If ionic mark 1 only cond 2 bp and 2 nbp around selenium [1] 1 bp and 3 nbp around both chlorine atoms [1]

(iii) the ionic compound

higher melting point / boiling point / less volatile conducts when molten or aqueous, covalent compound does not is soluble in water, covalent is not / ionic insoluble in organic solvents, covalent soluble in organic solvents harder any two [2] note there has to be comparison between the ionic compound and the covalent compound not density




(c) base [1] not alkali accepts a proton [2] accepts hydrogen ion / H+ only [1] proton and H+ [2] 3 (a) any four max 4

carbon forms carbon dioxide / carbon monoxide [1] this is a gas it escapes / blown out / diffuses [1] silicon forms silicon(IV) oxide / silica [1] / silicon(IV) oxide present in impure iron silicon(IV) oxide reacts with calcium oxide to form slag or calcium silicate [1] slag removed from surface [1] accept skimmed, syphoned, poured off not tapped max [4] accept correct formula or equations not calcium oxide reacts with silicon

(b) (i) any sensible suggestion – harder/stronger/can be tailored for a specific use/more

resistant to corrosion [1] not steel does not rust (ii) mild steel – cars or any vehicle/bicycles/white goods/screws or nails/roof/bridges/tools/

buildings/ships/pipes/machinery etc. [1] stainless steel – chemical plants/cooking utensils/jewellery/cutlery/surgical equipment/

kitchen sinks/pipes/etc. [1] (c) (i) strong attractive forces / strong bonds / bonds hard to break / requires a lot of

energy to break bonds [1] not between ions, not between positive and negative ions, not between electrons between positive ions and (negative) electrons / opposite charges attract [1]

(ii) because the layers, lattice or rows of ions/cations [1]

accept sheets of ions not atoms / molecules / protons / nuclei can move / slip / slide past each other [1]

4 (a) (i) 2ZnS + 3O2 → 2ZnO + 2SO2 [2] not balanced only [1] (ii) two reagents from named metal(s) more reactive than zinc/carbon monoxide [2] not hydrogen (iii) they have different boiling points [1] cadmium will distil first then zinc leaving lead/lead distilled last [1]




(b) for a high yield need low temperature [1] then rate would be too slow or uneconomic [1] a discussion of optimum temperature could score mark 1 and 2 presence of catalyst would increase rate (at same temperature) [1] does not alter the yield (at that temperature) [1] / economic rate at lower temperature, therefore higher yield higher pressure which would increase yield / rate [1] yield high enough / high pressure expensive [1] max [4] accept reverse arguments

note increase yield X position of equilibrium to right

5 (a) (i) 2Li + 2HI → 2LiI + H2 [1]

(ii) zinc carbonate + hydriodic acid → zinc iodide + carbon dioxide + water [1]

(iii) MgO + 2HI → MgI2 + H2O [1] (b) reaction 1 is redox / Li/2HI reaction [1] cond reason either oxidation number/state / electron transfer [1] (c) with hydriodic acid – iodine formed / goes dark brown / grey/black solid [1] not purple vapour not purple/black solution with hydrobromic acid – bromine formed / goes orange / yellow / brown / reddish brown / red

/ brown vapour [1] note can accept brown for iodine provided bromine is different orange/brown etc. (d) (i) the reaction is exothermic / reaction produces heat/energy [1] all the sodium hydroxide used up/neutralised / reaction has stopped [1] (ii) adding colder acid / no more heat produced [1] if not given in (d)(i) any comments such as “reaction has stopped” can gain mark (iii) 1.33 / 1.3 / 1.3333 (mol/dm3) scores both marks [2] not 1.34 for a correct method – M1 V1 / moles of NaOH = 0.02 with an incorrect answer only [1]




6 (a) (i) cracking / heat with catalyst [1] to make butane [1] butene reacts with steam/water / hydrated [1] accept heat and catalyst for cracking but if specified: 450 to 800°C zeolites / aluminosilicates / silica / aluminium oxide/alumina / china / broken pot / porcelain / chromium oxide

(ii) glucose / sugar changed to alcohol / ethanol [2]

accept an unbalanced equation (catalysed by) enzymes / yeast [1]

(b) butanoic acid [1] CH3-CH2-CH2-COOH [1] hydrogen atoms omitted from ends of bonds, penalise once (c) (i) ester [1] (ii) C6H12O2 ignore CH3COOC4H9 [1] (iii) correct structural formula of butyl ethanoate showing all bonds [2] 7 (a) metal A is magnesium [1] cond most reactive or fastest reaction [1] metal B is aluminium [1] cond faster reaction after removal of oxide layer / it would give more hydrogen / aluminium

more reactive than zinc [1] metal C is zinc [1] zinc least reactive [1] NOTE MAX [5] If you encounter different reasoning which is correct, please award the appropriate marks. (b) for magnesium and zinc same volume of hydrogen [1]

because both have valency of 2 / 1 mole of metal gives 1 mole of hydrogen / 1 mole of metal reacts with 2 moles of acid [1] bigger volume for aluminium because its valency is 3 / 1 mole of metal gives 1.5 moles of hydrogen / 1 mole of metal reacts with 3 moles of acid [1] If you encounter different reasoning which is correct, please award the appropriate marks. accept balanced equations accept ionic charges as alternative to valency




8 (a) addition – polymer only product / only one product [1] accept monomer has C=C accept monomer and polymer have same empirical formula accept no loss of material in polymerisation not only one monomer condensation – polymer and water / small molecule formed [1]

(b) -CH2 – CCl2- repeat unit correct [1] COND continuation [1] (c) CH2=CHOOCCH3 [1] (d) -OC(CH2)4CONH(CH2)6NH-

COND amide correct linkage [1] correct repeat units [1] continuation [1] not NH2 or COOH endings

[Total: 80]





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1 (i) Rb / Sr [1] (ii) I [1] (iii) Fe [1] (iv) P [1] (v) Si [1] 2 (a) (i) no reaction [1]

Fe + Sn2+ → Fe2+ + Sn / 2Fe + 3Sn2+ → 2Fe3+ + 3Sn [2] for realising that there would be a reaction shown by an attempt to write an equation e.g. writing Fe2Sn etc. allow [1] no reaction [1]

(ii) tin oxide, nitrogen dioxide (accept nitogen(IV) oxide/dinitrogen tetroxide), oxygen All three for two [2] accept correct formulae any two correct products [1] (b) (i) tin [1]

(ii) 4OH– → O2 + 2H2O + 4e– [2] not balanced allow [1] (iii) sulfuric acid [1] (c) zinc is more reactive than iron/steel [1]

tin is less reactive than iron/steel [1] zinc corrodes/reacts/loses electrons/is oxidised/is anodic/provides sacrificial protection/ forms positive ions (in preference to iron or steel) ORA allow iron is cathodic for this mark. [1] Iron/steel corrodes/reacts/rusts/loses electrons/is oxidised/is anodic/forms positive ions (in preference to tin). ORA allow tin is cathodic for this mark [1]




3 (a) (i) concentration of thiosulfate is proportional to volume of thiosulfate solution added (when total volume is same in all experiments) / concentration of acid always the same [2] for comments based on amount / to make experiments fair / comparable allow [1]

(ii) 240 s [1] (iii) decreases/reaction slower [1]

because concentration of thiosulfate decreases [1] frequency/chances/rate of collisions decreases [1] one mark can be scored for less/smaller amount/smaller volume of thiosulfate / less collisions

(b) rate increases with temperature (or at 42 °C) ORA [1]

particles/molecules/ions move faster or gain energy / ORA [1] (don’t accept reactants or atoms) more collisions / ORA [1] (last mark is for qualification of the collisions) i.e. greater frequency / more per unit time/more often /greater chance/more likely/more collision rate/more effective/more successful/more with activation energy / ORA [1]

4 One redox equation [1]

accept Fe2O3 + 3CO → 2Fe + 3CO2

2Fe2O3 + 3C → 4Fe + 3CO2

Fe2O3 + 3C → 2Fe + 3CO

C + O2 → CO2

CO2 + C → 2CO one acid/base equation [1]

CaO + SiO2 → CaSiO3

or CaCO3 + SiO2 → CaSiO3 + CO2 three more equations or comments [3] carbon burns to form carbon dioxide this reaction is exothermic or produces heat carbon dioxide is reduced to carbon monoxide carbon monoxide reduces hematite to iron carbon reduces hematite to iron limestone removes silica which is an impurity to form slag which is a waste product limestone decomposes or symbol/word equation




5 (a) Zn + H2SO4 → ZnSO4 + H2 / Zn + 2H+ → Zn2+ + H2 [2] marks are for correct reactants [1] correct products [1] If ionic equation is given don’t penalise SO4

2– spectator ions on both sides (b) (exothermic because) a cell produces (electrical) energy/electricity [1]

the next two marks score for electrons are lost AND gained / oxidation no. or state/valency both increases and decreases

/ two correct half equations i.e. Zn → Zn2+ + 2e– and 2H+ + 2e– → H2 [2] (c) zinc [1]

cond it is the more reactive metal / it supplies electrons / it forms ions more readily than iron [1]

(d) replace zinc with magnesium replace iron with copper use (more) concentrated sulfuric acid accept use a more concentrated acid / a more concentrated solution any two [2]




6 (a) (i) rate at which methanol formed by forward reaction [1] equals rate it is reacting in back reaction [1] rate of forward reaction equals rate of back reaction allow [1]

(ii) low/lower/decreased temperature [1]

high/higher/increased pressure [1] Explanations not needed but if they are given they must be correct IGNORE values of temperature and pressure

(iii) high pressure can be used / lower pressure due to expense or safety [1]

cannot use a low temperature as rate would be too slow the rate would not be economic [1]

(b) (i) ester [1] (ii) soap/sodium stearate or any acceptable salt/glycerol [1] (iii) burning both fuels forms carbon [1]

growing plants to make biodiesel removes carbon dioxide from atmosphere [1]

(c) (i) correct SF of an octane [1] (ii) add bromine (water)/bromine in an organic solvent [1]

result octane remains brown/orange/yellow/red [1] result octane goes colourless/decolourises [1] not clear/discolours colour of reagent must be shown somewhere for [3] otherwise max [2] accept equivalent test using KMnO4 in acid or alkali




7 (a) 3 bp and 1nbp around phosphorus [1] 1 bp and 3nbp around each chlorine [1]

(b) (i) PCl3 + 3H2O → 3HCl + H3PO3 [1] (ii) acid solutions same concentration [1]

measure pH/pH paper/Universal indicator [1] hydrochloric acid lower pH [1] colours of Universal indicator can be given as red<orange<yellow ignore precise pH values as long as HCl is lower than H3PO3 OR Acid solutions same concentration [1] add magnesium or any named metal above Hydrogen in reactivity series but not above magnesium calcium carbonate or any insoluble carbonate [1] hydrochloric acid react faster/shorter time [1] OR acid solutions same concentration [1] measure electrical conductivity [1] hydrochloric acid better conductor/bulb brighter [1] OR acid solutions same concentration [1] add sodium thiosulphate [1] hydrochloric acid forms precipitate faster/less time [1]

(iii) sodium hydroxide/sodium carbonate [1]

titration cond on correct reagent [1] second mark scores for mention of titration /burette/pipette/indicator. experimental detail not required any named soluble calcium salt e.g. calcium chloride/nitrate/hydroxide [1] precipitation/filter/decant/centrifuge [1]




8 (a) (i) (to avoid) carbon monoxide formation/so complete combustion occurs/avoid incomplete combustion So that CO2 is produced [1] CO does not dissolve/react with alkali [1]

(ii) CO2 is acidic [1] (iii) volume of gaseous hydrocarbon 20 cm3

volume of oxygen used = 90 cm3 [1] volume of carbon dioxide formed = 60 cm3 [1] no mark for 20 cm3 of hydrocarbon.

(iv) 2C3H6(g)/2CxHy(g) + 9O2(g) → 6CO2(g) + 6H2O(l) [1]

OR … C3H6(g) + 9/2O2(g) → 3CO2(g) + 3H2O(l) C3H6 [1] C3H6 can be given in the equation for the second mark

(b) (i) correct structural or displayed formula of another chlorobutane / dichlorobutane /

polychlorobutane [1] (ii) light / 200 °C / lead tetraethyl [1] (iii) cracking is the decomposition/breaking down of an alkane/hydrocarbon/petroleum [1]

heat/high temperature / Temperature between 450 °C to 800 °C OR catalyst / named catalyst [1] to give a simpler alkane and alkene [1] word equation or equation as example [1] to make polymers / to increase petrol fraction / organic chemicals/petrochemicals / hydrogen [1] any four





0620 CHEMISTRY








1 (i) Rb / Sr [1] (ii) I [1] (iii) Fe [1] (iv) P [1] (v) Si [1] 2 (a) (i) no reaction [1]

Fe + Sn2+ → Fe2+ + Sn / 2Fe + 3Sn2+ → 2Fe3+ + 3Sn [2] for realising that there would be a reaction shown by an attempt to write an equation e.g. writing Fe2Sn etc. allow [1] no reaction [1]

(ii) tin oxide, nitrogen dioxide (accept nitogen(IV) oxide/dinitrogen tetroxide), oxygen All three for two [2] accept correct formulae any two correct products [1] (b) (i) tin [1]

(ii) 4OH– → O2 + 2H2O + 4e– [2] not balanced allow [1] (iii) sulfuric acid [1] (c) zinc is more reactive than iron/steel [1]

tin is less reactive than iron/steel [1] zinc corrodes/reacts/loses electrons/is oxidised/is anodic/provides sacrificial protection/ forms positive ions (in preference to iron or steel) ORA allow iron is cathodic for this mark. [1] Iron/steel corrodes/reacts/rusts/loses electrons/is oxidised/is anodic/forms positive ions (in preference to tin). ORA allow tin is cathodic for this mark [1]




3 (a) (i) concentration of thiosulfate is proportional to volume of thiosulfate solution added (when total volume is same in all experiments) / concentration of acid always the same [2] for comments based on amount / to make experiments fair / comparable allow [1]

(ii) 240 s [1] (iii) decreases/reaction slower [1]

because concentration of thiosulfate decreases [1] frequency/chances/rate of collisions decreases [1] one mark can be scored for less/smaller amount/smaller volume of thiosulfate / less collisions

(b) rate increases with temperature (or at 42 °C) ORA [1]

particles/molecules/ions move faster or gain energy / ORA [1] (don’t accept reactants or atoms) more collisions / ORA [1] (last mark is for qualification of the collisions) i.e. greater frequency / more per unit time/more often /greater chance/more likely/more collision rate/more effective/more successful/more with activation energy / ORA [1]

4 One redox equation [1]

accept Fe2O3 + 3CO → 2Fe + 3CO2

2Fe2O3 + 3C → 4Fe + 3CO2

Fe2O3 + 3C → 2Fe + 3CO

C + O2 → CO2

CO2 + C → 2CO one acid/base equation [1]

CaO + SiO2 → CaSiO3

or CaCO3 + SiO2 → CaSiO3 + CO2 three more equations or comments [3] carbon burns to form carbon dioxide this reaction is exothermic or produces heat carbon dioxide is reduced to carbon monoxide carbon monoxide reduces hematite to iron carbon reduces hematite to iron limestone removes silica which is an impurity to form slag which is a waste product limestone decomposes or symbol/word equation




5 (a) Zn + H2SO4 → ZnSO4 + H2 / Zn + 2H+ → Zn2+ + H2 [2] marks are for correct reactants [1] correct products [1] If ionic equation is given don’t penalise SO4

2– spectator ions on both sides (b) (exothermic because) a cell produces (electrical) energy/electricity [1]

the next two marks score for electrons are lost AND gained / oxidation no. or state/valency both increases and decreases

/ two correct half equations i.e. Zn → Zn2+ + 2e– and 2H+ + 2e– → H2 [2] (c) zinc [1]

cond it is the more reactive metal / it supplies electrons / it forms ions more readily than iron [1]

(d) replace zinc with magnesium replace iron with copper use (more) concentrated sulfuric acid accept use a more concentrated acid / a more concentrated solution any two [2]




6 (a) (i) rate at which methanol formed by forward reaction [1] equals rate it is reacting in back reaction [1] rate of forward reaction equals rate of back reaction allow [1]

(ii) low/lower/decreased temperature [1]

high/higher/increased pressure [1] Explanations not needed but if they are given they must be correct IGNORE values of temperature and pressure

(iii) high pressure can be used / lower pressure due to expense or safety [1]

cannot use a low temperature as rate would be too slow the rate would not be economic [1]

(b) (i) ester [1] (ii) soap/sodium stearate or any acceptable salt/glycerol [1] (iii) burning both fuels forms carbon [1]

growing plants to make biodiesel removes carbon dioxide from atmosphere [1]

(c) (i) correct SF of an octane [1] (ii) add bromine (water)/bromine in an organic solvent [1]

result octane remains brown/orange/yellow/red [1] result octane goes colourless/decolourises [1] not clear/discolours colour of reagent must be shown somewhere for [3] otherwise max [2] accept equivalent test using KMnO4 in acid or alkali




7 (a) 3 bp and 1nbp around phosphorus [1] 1 bp and 3nbp around each chlorine [1]

(b) (i) PCl3 + 3H2O → 3HCl + H3PO3 [1] (ii) acid solutions same concentration [1]

measure pH/pH paper/Universal indicator [1] hydrochloric acid lower pH [1] colours of Universal indicator can be given as red<orange<yellow ignore precise pH values as long as HCl is lower than H3PO3 OR Acid solutions same concentration [1] add magnesium or any named metal above Hydrogen in reactivity series but not above magnesium calcium carbonate or any insoluble carbonate [1] hydrochloric acid react faster/shorter time [1] OR acid solutions same concentration [1] measure electrical conductivity [1] hydrochloric acid better conductor/bulb brighter [1] OR acid solutions same concentration [1] add sodium thiosulphate [1] hydrochloric acid forms precipitate faster/less time [1]

(iii) sodium hydroxide/sodium carbonate [1]

titration cond on correct reagent [1] second mark scores for mention of titration /burette/pipette/indicator. experimental detail not required any named soluble calcium salt e.g. calcium chloride/nitrate/hydroxide [1] precipitation/filter/decant/centrifuge [1]




8 (a) (i) (to avoid) carbon monoxide formation/so complete combustion occurs/avoid incomplete combustion So that CO2 is produced [1] CO does not dissolve/react with alkali [1]

(ii) CO2 is acidic [1] (iii) volume of gaseous hydrocarbon 20 cm3

volume of oxygen used = 90 cm3 [1] volume of carbon dioxide formed = 60 cm3 [1] no mark for 20 cm3 of hydrocarbon.

(iv) 2C3H6(g)/2CxHy(g) + 9O2(g) → 6CO2(g) + 6H2O(l) [1]

OR … C3H6(g) + 9/2O2(g) → 3CO2(g) + 3H2O(l) C3H6 [1] C3H6 can be given in the equation for the second mark

(b) (i) correct structural or displayed formula of another chlorobutane / dichlorobutane /

polychlorobutane [1] (ii) light / 200 °C / lead tetraethyl [1] (iii) cracking is the decomposition/breaking down of an alkane/hydrocarbon/petroleum [1]

heat/high temperature / Temperature between 450 °C to 800 °C OR catalyst / named catalyst [1] to give a simpler alkane and alkene [1] word equation or equation as example [1] to make polymers / to increase petrol fraction / organic chemicals/petrochemicals / hydrogen [1] any four





0620 CHEMISTRY




• Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the October/November 2011 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.





1 (a) (i) lithium oxide / strontium oxide [1] (ii) sulfur dioxide / nitrogen dioxide [1] (iii) aluminium oxide [1] (iv) carbon monoxide [1] accept: correct formulae (b) sulfur dioxide [1] burn (fossil) fuel containing sulfur / volcanoes [1] nitrogen dioxide [1] reaction of nitrogen and oxygen [1] high temperatures / in car engine [1] not: exhaust (c) (i) strontium oxide [1] accept: aluminium oxide (ii) use correct formula [1] cond: charges on ions 6x and 2o around oxygen [1] ignore: electrons around Li 2 (a) (i) (waste gases) from animals [1] decaying vegetation / anaerobic decay [1] accept: decomposition of organic material / natural gas (ii) carbon dioxide [1] water [1] (b) photosynthesis removes carbon dioxide from the atmosphere [1] both respiration and combustion produce carbon dioxide [1] any two of the following: [2]

plants photosynthesis changes carbon dioxide into carbohydrates (burning) of fossil fuels / named fuel / petrol / alkanes respiration by living organisms to obtain energy from carbon–containing compounds comment that the balance between these processes determines the percentage of carbon dioxide




3 (a) (i) bauxite [1] (ii) lowers melting point [1] better conductor / reduces amount of energy needed / reduces cost / more

economic / makes process viable / conserves energy [1] (iii) aluminium more reactive than copper / aluminium higher in reactivity series [1] hydrogen not aluminium formed at cathode [1] (b) Al 3+ + 3e → Al [1] 2O2– → O2 + 4e [2] note: not balanced = 1 oxygen reacts with carbon (anode) to form carbon dioxide / C + O2 → CO2 [1] note: if mark(s) for an electrode reaction are not awarded then allow aluminium ions accept

electrons / are reduced [1] oxide ion loses electrons / is oxidised [1] max 4 (c) (i) protective oxide layer [1] (ii) aluminium low density / light [1] aluminium is a good conductor [1] strength / prevent sagging / allows greater separation of pylons / core made of

steel because it is strong [1] 4 (a) rate of forward reaction equals rate of back reaction [1] concentrations do not change / macroscopic properties remain constant (with time) [1] accept: amounts (b) (i) increase [1] reaction 2 [1] Vr > Vp [1] (ii) same [1] reaction 1 [1] Vr = Vp [1] (iii) decrease [1] reaction 3 [1] Vp > Vr [1] accept: moles of gas / molecules of gas as an alternative to volume




5 (a) (i) rate of reaction decreases / gradient decreases [1] because concentration of bromine decreases [1] reaction stops because all bromine is used up [1] (ii) initial rate greater / gradient greater [1] because bigger surface area / more particles of iron exposed [1]

or: final mass the same [1]

because mass of bromine is the same so the same mass of iron is used [1] (iii) increase / decrease / change rate of stirring / not stirred [1] measure new rate / compare results [1] (b) (i) Fe to Fe2+ [1] because oxidation is electron loss / increase in oxidation number [1] (ii) Fe [1] (c) add sodium hydroxide solution / ammonia(aq) [1] Fe2+ green precipitate [1] Fe3+ brown precipitate [1] 6 (a) (i) correct structural formula of ethanoic acid [1] allow: –OH not: –COOH (ii) correct structural formula of ethanol [1] allow: –OH (b) (i) ethyl ethanoate [1] (ii) –OC6H4COOCH2CH2O– correct ester linkage [1] correct repeat units [1] continuation [1] accept: boxes if it is clear what the box represents (iii) any two from: long time to decay landfill sites visual pollution / litter danger to animals poisonous gases when burnt [2] accept: any correct suggestion




(c) synthetic – only two monomers [1] protein – many different monomers [1] or: protein has 1 C=O and 1N–H [1] nylon has 2 C=O / 2N–H [1] or: synthetic – one monomer is a dicarboxylic acid and the other is a diamine [1] protein all monomers are amino acids [1] 7 (a) (i) any Group 1 metal [1] accept: LiOH (ii) Cu(OH)2 → CuO + H2O [2] note: products only = 1 (iii) reactivity of metals / metals have different reactivities [1] (b) (i) zinc oxide, nitrogen dioxide, oxygen [2] note: two correct = 1 (ii) 2KNO3 → 2KNO2 + O2 [2] note: unbalanced = 1, correct word equation = 1 (c) calculation: Mr for NaHCO3 = 84 g; Mr for Na2O = 62 g; Mr for NaOH = 40 g Mr for Na2CO3 = 106 g (i) number of moles of NaHCO3 used = 3.36/84 = 0.04 [1] (ii) if residue is Na2O, number of moles of Na2O = 2.12/62 =0.034 / 0.03 if residue is NaOH, number of moles of NaOH = 2.12/40 = 0.053 / 0.05 if reside is Na2CO3, number of moles of Na2CO3 = 2.12/106 =0.02 all three correct [2] note: two correct = 1 (iii) equation 3 [1] mole ratio 2:1 agrees with equation [1]





0620 CHEMISTRY









1 (a) 27p 32n 27e [1] 27p 32n 25e [1] (b) (i) same proton number / same number of protons / same atomic number [1]

different nucleon number / different number of neutrons / different mass number [1] (ii) same electron distribution [1] allow: same proton number and same number of electrons not: same number of electrons / same number of shells (iii) industrial detection of leaks / thickness of paper etc. / nuclear fuel for generating

electricity / nuclear weapons / radiographs of welds / measuring wear / sterilising food [1] not: carbon dating

medical treatment of cancer, radiotherapy, treatment of thyroid gland, X rays, tracer studies in body, sterilising equipment, locating tumours

accept: X-rays only once [1] 2 (a) burns to form sulfur dioxide [1] acid rain / any problem associated with acid rain / sulfur dioxide is poisonous [1] (b) (i) bigger surface area [1] burns / reacts faster / greater number of collisions [1] not: more sulfur dioxide (ii) kills microbes / bacteria / fungi etc. [1] accept: anti-oxidant / stops oxygen oxidising juice / prevents growth of bacteria (iii) bleach / refrigerant / making wine / fumigant /insecticide / dyes [1] not: making sulfuric acid (c) 2SO2 + O2 � 2SO3 [1] temperature 400 to 450

oC [1] pressure 1 to 10 atmospheres [1] catalystvanadium(V) oxide / vanadium oxide [1] (d) SO3 + H2SO4 � H2S2O7 [1] H2S2O7 + H2O � 2H2SO4 [1]




3 (a) (i) heat / roast in air / oxygen [1] accept: burn in air / oxygen (ii) (reduce) with carbon / carbon monoxide [1]

(b) test it with both hydrochloric acid and sodium hydroxide(aq) [1] accept: any named strong acid and any strong alkali if only acid and alkali given then max = 3 basic oxide reacts with acid [1] acidic oxide reacts with alkali/base [1] amphoteric reacts with both [1] accept: for react – form salt and water

(c) (i) at equilibrium [1]

rate of forward reaction equals rate of back reaction / concentrations remain constant / macroscopic properties do not change with time [1] accept: amounts do not change with time

(ii) equilibrium moves to left (SbOCl used up) [1]

hydrochloric acid removed by reacting with SbOCl precipitate dissolves in hydrochloric acid

(iii) add water / dilute / add an alkali / add more SbCl3 / add a base / add a carbonate [1] 4 (a) (i) ScF3 [1]

correct charges [1] 7o and 1x around fluorine [1]

(ii) strong forces / bonds between ions [1]

accept: lattice as alternative to bonds / requires a lot of energy to break bond between ions not: giant molecular / IMFs (b) (i) 1Si surrounded by 4O [1] 1O surrounded by 2Si [1] looks or stated to be tetrahedral [1] (ii) silicon(IV) oxide does not conduct and (molten) scandium fluoride

does conduct [1] not: good and poor (iii) scandium fluoride contains ions (silicon(IV) oxide does not) [1]

ions can move when molten or in solution [1]




5 (a) CH3-CH2-CH2-CH2-CH2-OH [1] 88 [1] 156 to159

oC [1] (b) any two from: (same) general (molecular) formula

same functional group consecutive members differ by –CH2 common methods of preparation

(c) correct structure and 4bp around carbon [1] 2bp and 2nbp around oxygen [1] 1bp on hydrogens [1] (d) (i) correct structural formula for propanoic acid [1] allow: OH but all other bonds to be shown (ii) air / oxygen [1] bacteria / microbes / micro-organisms [1] accept: mother of vinegar not: yeast (e) propyl ethanoate [1] allow: CH3COOC3H7 not: C5H10O2 [1]




6 (a) (i) to neutralise all the acid / so all acid reacts [1] not: reaction goes to completion (ii) remove excess carbonate / removes unreacted carbonate [1] not: remove solid (iii) need water of crystallisation / hydrated crystals / to get crystals [1] (iv) filter / decant / wash crystals [1] dry with filter paper or tissues etc. [1] accept: in warm oven / warm place / in sun not: just heat

(b) (i) potassium carbonate is soluble / both salts soluble [1] (ii) use potassium carbonate solution [1] accept: implication of solution – in pipette / burette / 25 cm3 titrate / titration term required [1] use an indicator accept: any named acid/base indicator [1] repeat without indicator / use carbon to remove indicator [1] (c) mass of hydrated magnesium sulfate = 1.476 g

mass of barium sulfate formed = 1.398 g the mass of one mole of BaSO4 = 233 g the number of moles of BaSO4 formed = 0.006 [1] the number of moles of MgSO4.xH2O used in experiment = 0.006 [1] the mass of one mole of MgSO4.xH2O = 1.476/0.006 = 246 g [1] the mass of xH2O in one mole of MgSO4.xH2O = 246 – 120 = 126 g [1] x = 126/18 = 7 [1] if x given without method = max 1 note: apply ecf but x must be an integer and less than 10




7 (a) fraction is the distillate collected [1] between 40–100

oC / in the stated range [1] (b) (i) C8H18 + 25/2O2 � 8CO2 + 9H2O [2]

accept: double the above / 12.5 in front of oxygen

(ii) poisonous / toxic / damages health / brain / kidneys [1] note: must relate to people

not: just harmful (iii) dibromo 2 bromine atoms (per molecule)

not: Br2

accept: 2 bromide groups eth 2 carbon atoms (per molecule)

ane a C-C single bond / no C=C / group CnH2n+1 / saturated ignore: any reference to alkanes all three correct [2] two correct only [1] [2]

(iv) position of bromine atom(s) [1]

(c) 0.104/0.026 [1]

n = 4 [1]

(d) (oxides of nitrogen) change carbon monoxide into carbon dioxide [1] oxides of nitrogen then become nitrogen [1] (oxides of nitrogen) change hydrocarbons into carbon dioxide and water [1] accept: balanced equations for first two marks

2NO + 2CO � N2 + 2CO2 and 2NO � N2 + O2 [2] oxygen changes hydrocarbons into carbon dioxide and water [1]





0620 CHEMISTRY









1 (a) (i) Cs / Fr [1] (ii) Br [1] (iii) U / Pu / Th [1]

(iv) I or At [1] (v) As [1] (vi) He / Ne / Ar / Kr / Xe [1] (b) (i) GeO2 / GeO [1] (ii) TeBr2 / TeBr4 [1] (c) (i) Sr2+ [1]

(ii) F– [1] 2 (a) (i) molecule / unit / simple compound / building block and used to make a

polymer / big molecule / long chain / macromolecule [1] formation of a polymer / big molecule / long chain / macromolecule or joining of

monomers and elimination / removal / formation of a simple or small molecule / H2O / HCl [1]

note: two points needed for 1 mark in both parts (ii) -O- linkage [1] three correct monomer units [1] continuation [1] (b) (i) catalyst and from living organism [1] accept: biological catalyst / protein catalyst (ii) enzyme denatured / destroyed [1] (iii) chromatography [1] locating agent / description of locating agent [1] measure Rf / compare with standards [1]




3 (a) sodium hydroxide solution [1] warm [1] (only) ammonium phosphate gives off ammonia / gas (which will turn red litmus paper

blue) [1] or: sodium hydroxide solution [1] dissolve fertiliser in water [1] Ca2+ gives (white) ppt [1] or: flame test [1] Ca2+ brick red / orange / orange-red [1] NH4

+ no colour [1] (b) iron catalyst [1] pressure 150–300 atmospheres [1] temperature 370–470 °C [1]

N2 + 3H2 ⇌ 2NH3 [1]

note: units required for temperature and pressure (c) potassium / K [1] (d) (i) needs to be soluble / in solution (to be absorbed by plants) [1] (ii) base [1] proton acceptor [1] (e) plant growth depends on soil acidity or pH / plants have optimum pH (for growth) [1] add Ca(OH)2 / CaO / CaCO3 / lime / slaked lime / quicklime / limestone [1] 4 (a) (i) alloy / mixture [1] iron and carbon / another metal or element etc. [1] (ii) electron loss [1] (b) electrons move from / lost from Mg [1] to steel / iron [1] (c) (i) 2H+ + 2e → H2 [2] not balanced = 1




(ii) sacrificial protection – is a cell [1] cathodic protection – is electrolysis NOT electrical cell [1] or: sacrificial protection – electrons from more reactive metal [1] cathodic protection – electrons from battery etc. [1] or: sacrificial protection – does not need or use power / battery / electricity / electrical

cell [1] cathodic protection – does [1] or: sacrificial protection uses up / needs a sacrificial / more reactive metal [1] cathodic protection doesn’t [1] 5 (a) light / UV / sun / sunlight / solar energy [1] starts / initiates / speeds up [1] (b) (i) 0.03 % – 1(%) carbon dioxide [1] accept: less than 1(%) 20 % – 21(%) oxygen [1] (ii) remove carbon dioxide from atmosphere [1] produce oxygen [1] any two from: photosynthesis chlorophyll / chloroplast light / sun / sunlight / UV / photochemical formed carbohydrates / glucose / sugar(s) [2] (c) reaction is photochemical / needs light [1] (light) causes formation of silver / silver ions reduced [1] (on formation of silver) goes black [1] no light still silver(I) bromide / stays white / no reaction [1] 6 (a) any three from: barium more reactive / forms ions more readily barium reacts with (cold) water, nickel does not barium more vigorous with acids nickel compounds coloured, barium compounds white nickel has more than one oxidation state, barium has one nickel / nickel compounds catalysts, barium / barium compounds not catalysts nickel forms complex ions, barium does not [3] (b) (i) forward reaction favoured by low temperatures / reverse reaction favoured by

high temperatures / heat [1] exothermic [1] (ii) products / RHS [1] has fewer moles / molecules / smaller volume / ORA [1] (iii) do not react or left behind / left at 60

oC [1]




(iv) electrolysis [1] cathode (pure) nickel [1] anode impure nickel [1] electrolyte is a soluble nickel salt [1] 7 (a) correct method shown

i.e. 126/14 (= 9) or 14x = 126 or x = 9 or (12 × 9) + 18 = 126 [1] C9H18 note: correct formula only = 1 [1] (b) (i) all hydrogen atoms 1bp [1] C—C bond atoms 1bp [1] C=C 2 bp [1] (ii) correct repeat unit [1] continuation [1] (iii) bonds broken H-H +436 (kJ/mol) C=C +610 = +1046 (kJ/mol) [1] bonds formed

2C-H –415 × 2 kJ/mol C-C –346 = –1176 (kJ/mol) [1] –130 kJ/mol / more energy released than absorbed [1] or: bonds broken 3882 (kJ/mol) [1] bonds formed 4012 (kJ/mol) [1] –130 kJ/mol / more energy released than absorbed [1] allow: ecf for final mark as long as the answer is not positive note: units not necessary (c) (i) butan-1-ol or butan-2-ol or butanol [1] (ii) CH3-CH2-CH(Br)-CH2Br [2] C4H8Br2 = 1 note: any other dibromobutane = 0

(iii) HI [1]





0620 CHEMISTRY









1 (a) (i) evaporation / boiling / vaporisation / evaporate / vaporise; [1] condensation / liquefaction / condense / liquefy; [1] (ii) condensation accept: correct equation H2O(g)→H2O(l)

because energy / heat is given out / gas has more energy than liquid / need to supply energy to change liquid to gas so reverse must give out energy / bonds form; [1]

(b) chlorination / chlorine to kill microbes; [1]

filtration or filter; [1] accept: sedimentation or sand or gravel or grit

(c) (i) combustion of fossil fuels; [1]

(which contain) sulfur; [1] sulfur dioxide formed; [1] (reacts in air / with water to form) sulfurous / sulfuric acid; [1] OR nitrogen and oxygen in air; [1] react at high temperatures / in engines; [1] to form oxides of nitrogen or named oxide of nitrogen; [1] (reacts in air / with water to form) nitrous / nitric acid; [1] [max 4]

(ii) calcium oxide is soluble in water / reacts with water to form

calcium hydroxide; [1] pH above 7 / the water becomes alkaline; [1] OR calcium carbonate insoluble in water; [1] pH cannot be above 7 / water is neutral / does not make water alkaline; [1] [max 2] [Total: 11] 2 (a) nitric acid; [1]

sodium hydroxide / carbonate / hydrogen carbonate; [1]

copper(II) oxide / hydroxide / carbonate; [1] any named soluble chloride; [1] accept: hydrochloric acid / hydrogen chloride silver(I) nitrate / ethanoate / sulfate; [1] must be soluble silver salt not silver oxide / carbonate

zinc(II) sulfate [1]

(b) (i) Ag+(aq) + Cl –(aq) → AgCl(s) [2]

equation correct state symbols missing [1]

(ii) ZnCO3 + H2SO4 → ZnSO4 + CO2 + H2O [2] correct formula for zinc sulfate = 1

[Total: 10]




3 (a) (i) decrease down group; [1] (ii) caesium / francium; [1] (iii) 2Rb + 2H2O → 2RbOH + H2 [2] not balanced = [1] (b) (i) Li+ [1] (ii) N3– [1] (iii) regular arrangement of ions / particles / positive and negative ions alternate; [1]

not: atoms (iv) 3:1; [1] ratio to balance charges / reason in terms of valency; [1] [Total: 9] 4 (a) 2 + 8 + 11 + 2 [1] (b) hard;

strong / high tensile strength; high mp / bp / high fixed points; high density; [2]

three properties = [2] two properties = [1] not: properties of all metals e.g. good conductor, lustre etc. or form coloured compounds

(c) catalyst would not affect yield / change position of equilibrium / affects both sides equally; [1]

(higher) temperature would reduce yield / increase in temperature would favour back reaction; [1]

(d) (i) V3+ is oxidant; [1] (ii) V3+ to V4+; [1]

increase in oxidation number / electron loss; [1] [Total: 8]

5 (a) calcium carbonate → calcium oxide + carbon dioxide [1] accept: correct symbol equation

Ca(OH)2 → CaO + H2O [1]

(b) (i) CuO and NO2 and O2; [1]

accept: names or correct formulae




(ii) 2NaNO3 → 2NaNO2 + O2 [2] accept: NaNO3 → NaNO2 + 1/2 O2 not balanced = [1]

(c) Na / Ca; [1] (d) Cu; Ag; [2]

accept: ions Cu2+ and Ag+ [Total: 8] 6 (a) 10 cm3; [1] 65 cm3; [1] (b) (i) chlorination / substitution / photochemical / exothermic / halogenation / free radical; [1] (ii) (compounds) same molecular formula; different structural formulae; [2] (iii) CH3–CH2–CH2–CH2–Cl [1]

CH3–CH2–CH(Cl)–CH3 [1] (c) (i) potassium manganate(VII) / potassium dichromate(VI) / copper(II) oxide; [1] note: do not insist on oxidation numbers but if given must be correct (ii) butanoic acid; [1] (iii) butyl ethanoate; [1] correct formula all bonds shown = [2] if alkyl groups incorrect then correct ester linkage showing bonds = [1] [2] [Total: 12]




7 (a) burning produces toxic gases / harmful to health increases greenhouse gases / global warming reduces visual pollution / litter reduces risks to wildlife shortage of landfill sites / reduces space needed in landfill sites / saves space non-biodegradable / long time to rot / decompose / accumulates waste burning source of energy / used to generate electricity

recycling conserves petroleum / natural resources difficult to recycle / expensive / takes much energy problems over sorting reduces need for landfill quality of plastic is reduced each time it is recycled four DIFFERENT valid points which are advantages or disadvantages of burning and/or recycling [4]

(b) (i) addition (polymerisation); [1]

(polymer) only product / no by-products; [1] condensation (polymerisation); [1]

(polymer and) simple molecule / water / hydrogen chloride / one other product forms; [1]

(ii) a correct linkage (for a polyamide / polyester); [1] two different monomers; [1] [Total: 10] 8 (a) (i) device which changes chemical energy; [1] into electrical energy; [1] OR produces a voltage / potential difference / electricity; [1] due to difference in reactivity of two metals; [1]

OR produces a voltage / potential difference / electricity; [1] by redox reactions; [1] (ii) negative / electrode B / right electrode; [1]

accept: anode because it is the electrode which supplies electrons to external circuit loses ions / iron ions / Fe2+ or Fe3+; [1] electrons move from this electrode; [1]

(iii) change of mass of electrode / mass of rust formed; [1] time / mention of stop watch / regular intervals; [1] (iv) to make it a better conductor; [1]




(b) moles of Fe = 51.85/56 = 0.926 (0.93); [1] moles of O = 22.22/16 = 1.389 (1.39); [1] moles of H2O = 16.67/18 = 0.926 (0.93); [1]

if given as 0.9 1.4 0.9 three of the above correct = [2] two of the above correct = [1] simplest whole number mole ratio Fe : O : H2O is 2: 3: 2 / Fe2O3.2H2O; [1] allow: ecf for a formula based on an incorrect whole number ratio [Total: 12]





0620 CHEMISTRY









1 (a) neon has full outer shell / energy level / valency shell / octet / 8 (electrons) in outer shell / neon does not need to lose or gain electrons; [1] fluorine atoms have 7 electrons / needs 1 to fill / has incomplete shell / forms bonds with other fluorine atoms / fluorine (atoms) form covalent bonds / shares electrons; [1]

(b) atomic number / proton number / number of protons (in one atom); [1] (c) weak intermolecular (or between molecules) forces / Van der Waals forces between

molecules / low amount of energy required to break bonds between molecules; [1] strong bonds don’t break / covalent bonds don’t break / (unnamed) bonds within molecules / between atoms don’t break; [1]

(d) 1 non-bonding pair on each nitrogen atom; [1]

6 electrons between nitrogen atoms; [1] 2 (a) weak forces between layers or between (hexagonal) rings / weak bonds between layers or

between (hexagonal) rings / Van der Waals forces between layers or between (hexagonal) rings; [1] (layers/rings) slip/slide (over each other) / move over each other [1]

(b) strong bonds (between atoms) / covalent bonds (between atoms); [1]

all bonds are covalent/strong / each atom covalently bonded / carbon (atoms) is bonded to four others / bonds are directional / (atoms are arranged) tetrahedrally; [1]

accept: carbon has four bonds (c) graphite has delocalised / mobile / free electrons; [1]

diamond (outer shell) electrons used / fixed / localised in bonding / no delocalised electrons / no mobile electrons / no free electrons; [1]

3 (a) flexible / easily form different shapes / easily moulded / bends (without cracking); [1]

non-biodegradable / unreactive / don’t corrode / prevent corrosion / prevent oxidation (of the conducting metal) / water resistant / waterproof; [1]

(b) improve appearance / decorative / makes appearance shiny; [1]

prevent corrosion / rusting / protect steel / chromium will not corrode / chromium is not oxidised / chromium protected by an oxide layer; [1]

(c) low density / light / protected by oxide layer / no need to paint / resists corrosion / (high)

strength / strong;; any two [2] note: high strength to weight ratio = 2

(d) high mpt / withstands high temperature / good conductor (of heat) / heats up quickly /

malleable / ductile / resists corrosion / good appearance / unreactive (or example of lack of reactivity e.g. does not react with food or water or acid or air);; any two [1]




(e) (lattice) positive ions / cations / metal ions and sea of electrons / delocalised or free or mobile or moving electrons; [1] attraction between positive ions and electrons; [1]

4 (a) (i) oxygen; [1]

carbon dioxide / fluorine / carbon monoxide; [1] (ii) decrease mpt (of alumina/Al2O3) / lower (operating) temperature (from 1900/2100 (°C) to

800/1000 (°C) / reduce energy (accept heat or electrical) requirement; [1] improve conductivity / dissolves the Al2O3 / acts as solvent; (allow: makes aluminium oxide conduct / to conduct electricity / making ions free to move) [1]

(iii) Al2O3 (accept alumina) reacts / dissolves / forms a salt and water / is neutralised; [1]

(Fe2O3 removed by) filtration / centrifugation / decantation; [1] (b) (i) electrolysis / electrolyte / electrodes / anode / cathode / electricity / cell; [1]

chlorine formed at anode (positive electrode); (note: can be awarded from a correct or incorrect equation with Cl2 as the only substance on the right as long as anode is mentioned.) [1] hydrogen formed at cathode (negative electrode); (note: can be awarded from a correct or incorrect equation with H2 as the only substance on the right as long as cathode is mentioned.) [1]

one correct half equation either 2Cl – → Cl2 + 2e or 2H+ + 2e → H2 [1]

solution remaining contains Na+ and OH– / sodium and hydroxide ions / NaOH / sodium hydroxide left behind/remains in solution; [1] note: if a mercury cathode is specified

electrolysis / electrolyte / electrodes / anode / cathode / electricity / cell; [1] chlorine formed at anode (positive electrode); (note: can be awarded from a correct or incorrect equation with Cl2 as the only substance on the right as long as anode is mentioned.) [1] sodium formed at cathode; (note: can be awarded from a correct or incorrect equation with Na as the only substance on the right as long as cathode is mentioned.) [1]

one correct half equation at anode i.e. 2Cl – → Cl2 + 2e or at cathode Na+ + e → Na

(accept: equivalent with NaHg amalgam) [1] NaOH/sodium hydroxide is formed by sodium/sodium mercury amalgam reacting with or when added to water; [1] note: award the fourth and fifth mark if correct equation given for reaction between sodium or sodium mercury amalgam reacting with water i.e.

2Na(Hg) + 2H2O → 2NaOH + H2 + (2Hg)

(ii) H2 / H / hydrogen and making ammonia / making margarine / hardening fats / fuel /

energy source / cryogenics / welding; [1] Cl2 / Cl / chlorine and (making) bleach / water treatment / kill bacteria (in water) / water purification / swimming pools / making solvents / making PVC / making weed killer / making disinfectants / making hydrochloric acid / HCl / making herbicides / pesticides / insecticides; [1]




5 (a) (i) correct -O- linkage; [1] correct unit and continuation -O-�- (minimum); [1]

(ii) any name or correct formula of a (strong) acid / H+; [1] (iii) contain carbon hydrogen and oxygen /C, H and O; [1]

(b) (i) glucose → ethanol + carbon dioxide [1] (ii) yeast is catalyst / provides enzymes / speeds up reaction / too slow without yeast; [1]

yeast cells grow / multiply / reproduce / undergo budding / breed; [1] (iii) heat or high temperature would kill yeast (cells) / heat or high temperature denatures

enzymes; [1] not: enzyme killed / denatures yeast reduces rate of reaction / slows reaction / (yeast or enzyme) no longer catalyses / no catalyst / stops reaction / no more product; [1]

(c) (i) would produce carbon dioxide or carboxylic or organic acids (if oxygen is present) / to

prevent aerobic respiration / so products are not oxidised / anaerobic bacteria can’t live with oxygen; [1]

(ii) fossil fuels have a reduced need / conserved / no need to import / will last longer /

cracking hydrocarbons to make methane no longer required; (methane) is renewable / carbon neutral;

reduce pollution of water or sea / prevents visual pollution / prevents need for waste disposal or accumulation (accept: any methods of waste disposal) / so that waste is recycled; any two [2]

6 (a) (i) A C D B [1] (ii) speed (or rate) increases as concentration increases / time decreases as concentration

increases; [1] rate or speed or time depends on (concentration) of H+ or hydrogen ions; [1] B is slow because propanoic acid is weak or doesn’t dissociate or weakly ionises; or B is slow because HCl and H2SO4 are stronger or ionise or dissociate more than propanoic; [1] D slower than C because C is more concentrated than D / ORA; [1] A is fast because H+ concentration high (note: this would also score second mark if not already awarded) / H2SO4 is diprotic or dibasic or 2H+; [1] time is inversely proportional to rate / owtte / ORA; [1] max [5]




(b) change 1: increase temperature / heat (the mixture); [1]

particles/molecules/ions have more energy or move faster; [1] more (successful) collisions / more particles with Ea; [1] change 2: increase surface area / decrease particle size / use powdered (magnesium) / use smaller pieces / crush the magnesium; [1] more collisions / more particles exposed to reaction; [1]

or catalyst; [1]

more (successful) collisions; [1] lowers Ea; [1] max [5]

7 (a) (i) CH2/H2C [1] (ii) same ratio of C:H (atoms) / all cancel to CH2 / because general formula is CnH2n / same

ratio of atoms or elements (in the compound) / C:H ratio is 1:2; [1] (b) (i) propanoic / propionic (acid); [1]

ethanoic / acetic (acid); [1] (ii) formula of ethene / but-2-ene / any symmetrical alkene; [1] (c) (i) CH3CH(Br)CH2Br [1] (ii) CH3CH(OH)CH3 / CH3CH2CH2OH / C3H7OH [1] (d)

correct unit; [1] accept: more than one repeat unit continuation bonds at both ends; [1]

(e) if C5H10 is given award 3 marks;;; [3]

if C10H20 is given award 2 marks;; if 1:7.5:5 / 2:15:10 is given award 2 marks;; in all other cases a mark can be awarded for moles of O2 (= 2.4/32 =) 0.075 AND moles of CO2 (= 2.2/44 =) 0.05;

2C5H10 + 15O2 → 10CO2 + 10H2O [1] accept: multiples including fractions allow: ecf for correct equation from any incorrect alkene




8 (a) proton donor; [1] (b) equal concentrations of both (solutions); [1]

add Universal indicator / determine pH / pH paper; [1] ethylamine has lower pH / ORA; [1] or equal concentration of both (solutions); [1] measure conductivity of aqueous ethylamine and sodium hydroxide; [1] ethylamine will have lower conductivity / sodium hydroxide will have higher conductivity; [1]

(c) add strong(er) base / NaOH / KOH; [1]

warm / heat; [1] (d) (ethylamine forms) hydroxide ions / OH– (in water); [1]

hydroxide ions / OH– reacts with iron(III) ions / Fe3+; or iron(III) hydroxide / Fe(OH)3 (forms as a brown precipitate); [1]

note: balanced or unbalanced ionic equation i.e. Fe3+ + (3)OH– → Fe(OH)3 scores both marks





0620 CHEMISTRY









1 (a) neon has full outer shell / energy level / valency shell / octet / 8 (electrons) in outer shell / neon does not need to lose or gain electrons; [1] fluorine atoms have 7 electrons / needs 1 to fill / has incomplete shell / forms bonds with other fluorine atoms / fluorine (atoms) form covalent bonds / shares electrons; [1]

(b) atomic number / proton number / number of protons (in one atom); [1] (c) weak intermolecular (or between molecules) forces / Van der Waals forces between

molecules / low amount of energy required to break bonds between molecules; [1] strong bonds don’t break / covalent bonds don’t break / (unnamed) bonds within molecules / between atoms don’t break; [1]

(d) 1 non-bonding pair on each nitrogen atom; [1]

6 electrons between nitrogen atoms; [1] 2 (a) weak forces between layers or between (hexagonal) rings / weak bonds between layers or

between (hexagonal) rings / Van der Waals forces between layers or between (hexagonal) rings; [1] (layers/rings) slip/slide (over each other) / move over each other [1]

(b) strong bonds (between atoms) / covalent bonds (between atoms); [1]

all bonds are covalent/strong / each atom covalently bonded / carbon (atoms) is bonded to four others / bonds are directional / (atoms are arranged) tetrahedrally; [1]

accept: carbon has four bonds (c) graphite has delocalised / mobile / free electrons; [1]

diamond (outer shell) electrons used / fixed / localised in bonding / no delocalised electrons / no mobile electrons / no free electrons; [1]

3 (a) flexible / easily form different shapes / easily moulded / bends (without cracking); [1]

non-biodegradable / unreactive / don’t corrode / prevent corrosion / prevent oxidation (of the conducting metal) / water resistant / waterproof; [1]

(b) improve appearance / decorative / makes appearance shiny; [1]

prevent corrosion / rusting / protect steel / chromium will not corrode / chromium is not oxidised / chromium protected by an oxide layer; [1]

(c) low density / light / protected by oxide layer / no need to paint / resists corrosion / (high)

strength / strong;; any two [2] note: high strength to weight ratio = 2

(d) high mpt / withstands high temperature / good conductor (of heat) / heats up quickly /

malleable / ductile / resists corrosion / good appearance / unreactive (or example of lack of reactivity e.g. does not react with food or water or acid or air);; any two [1]




(e) (lattice) positive ions / cations / metal ions and sea of electrons / delocalised or free or mobile or moving electrons; [1] attraction between positive ions and electrons; [1]

4 (a) (i) oxygen; [1]

carbon dioxide / fluorine / carbon monoxide; [1] (ii) decrease mpt (of alumina/Al2O3) / lower (operating) temperature (from 1900/2100 (°C) to

800/1000 (°C) / reduce energy (accept heat or electrical) requirement; [1] improve conductivity / dissolves the Al2O3 / acts as solvent; (allow: makes aluminium oxide conduct / to conduct electricity / making ions free to move) [1]

(iii) Al2O3 (accept alumina) reacts / dissolves / forms a salt and water / is neutralised; [1]

(Fe2O3 removed by) filtration / centrifugation / decantation; [1] (b) (i) electrolysis / electrolyte / electrodes / anode / cathode / electricity / cell; [1]

chlorine formed at anode (positive electrode); (note: can be awarded from a correct or incorrect equation with Cl2 as the only substance on the right as long as anode is mentioned.) [1] hydrogen formed at cathode (negative electrode); (note: can be awarded from a correct or incorrect equation with H2 as the only substance on the right as long as cathode is mentioned.) [1]

one correct half equation either 2Cl – → Cl2 + 2e or 2H+ + 2e → H2 [1]

solution remaining contains Na+ and OH– / sodium and hydroxide ions / NaOH / sodium hydroxide left behind/remains in solution; [1] note: if a mercury cathode is specified

electrolysis / electrolyte / electrodes / anode / cathode / electricity / cell; [1] chlorine formed at anode (positive electrode); (note: can be awarded from a correct or incorrect equation with Cl2 as the only substance on the right as long as anode is mentioned.) [1] sodium formed at cathode; (note: can be awarded from a correct or incorrect equation with Na as the only substance on the right as long as cathode is mentioned.) [1]

one correct half equation at anode i.e. 2Cl – → Cl2 + 2e or at cathode Na+ + e → Na

(accept: equivalent with NaHg amalgam) [1] NaOH/sodium hydroxide is formed by sodium/sodium mercury amalgam reacting with or when added to water; [1] note: award the fourth and fifth mark if correct equation given for reaction between sodium or sodium mercury amalgam reacting with water i.e.

2Na(Hg) + 2H2O → 2NaOH + H2 + (2Hg)

(ii) H2 / H / hydrogen and making ammonia / making margarine / hardening fats / fuel /

energy source / cryogenics / welding; [1] Cl2 / Cl / chlorine and (making) bleach / water treatment / kill bacteria (in water) / water purification / swimming pools / making solvents / making PVC / making weed killer / making disinfectants / making hydrochloric acid / HCl / making herbicides / pesticides / insecticides; [1]




5 (a) (i) correct -O- linkage; [1] correct unit and continuation -O-�- (minimum); [1]

(ii) any name or correct formula of a (strong) acid / H+; [1] (iii) contain carbon hydrogen and oxygen /C, H and O; [1]

(b) (i) glucose → ethanol + carbon dioxide [1] (ii) yeast is catalyst / provides enzymes / speeds up reaction / too slow without yeast; [1]

yeast cells grow / multiply / reproduce / undergo budding / breed; [1] (iii) heat or high temperature would kill yeast (cells) / heat or high temperature denatures

enzymes; [1] not: enzyme killed / denatures yeast reduces rate of reaction / slows reaction / (yeast or enzyme) no longer catalyses / no catalyst / stops reaction / no more product; [1]

(c) (i) would produce carbon dioxide or carboxylic or organic acids (if oxygen is present) / to

prevent aerobic respiration / so products are not oxidised / anaerobic bacteria can’t live with oxygen; [1]

(ii) fossil fuels have a reduced need / conserved / no need to import / will last longer /

cracking hydrocarbons to make methane no longer required; (methane) is renewable / carbon neutral;

reduce pollution of water or sea / prevents visual pollution / prevents need for waste disposal or accumulation (accept: any methods of waste disposal) / so that waste is recycled; any two [2]

6 (a) (i) A C D B [1] (ii) speed (or rate) increases as concentration increases / time decreases as concentration

increases; [1] rate or speed or time depends on (concentration) of H+ or hydrogen ions; [1] B is slow because propanoic acid is weak or doesn’t dissociate or weakly ionises; or B is slow because HCl and H2SO4 are stronger or ionise or dissociate more than propanoic; [1] D slower than C because C is more concentrated than D / ORA; [1] A is fast because H+ concentration high (note: this would also score second mark if not already awarded) / H2SO4 is diprotic or dibasic or 2H+; [1] time is inversely proportional to rate / owtte / ORA; [1] max [5]




(b) change 1: increase temperature / heat (the mixture); [1]

particles/molecules/ions have more energy or move faster; [1] more (successful) collisions / more particles with Ea; [1] change 2: increase surface area / decrease particle size / use powdered (magnesium) / use smaller pieces / crush the magnesium; [1] more collisions / more particles exposed to reaction; [1]

or catalyst; [1]

more (successful) collisions; [1] lowers Ea; [1] max [5]

7 (a) (i) CH2/H2C [1] (ii) same ratio of C:H (atoms) / all cancel to CH2 / because general formula is CnH2n / same

ratio of atoms or elements (in the compound) / C:H ratio is 1:2; [1] (b) (i) propanoic / propionic (acid); [1]

ethanoic / acetic (acid); [1] (ii) formula of ethene / but-2-ene / any symmetrical alkene; [1] (c) (i) CH3CH(Br)CH2Br [1] (ii) CH3CH(OH)CH3 / CH3CH2CH2OH / C3H7OH [1] (d)

correct unit; [1] accept: more than one repeat unit continuation bonds at both ends; [1]

(e) if C5H10 is given award 3 marks;;; [3]

if C10H20 is given award 2 marks;; if 1:7.5:5 / 2:15:10 is given award 2 marks;; in all other cases a mark can be awarded for moles of O2 (= 2.4/32 =) 0.075 AND moles of CO2 (= 2.2/44 =) 0.05;

2C5H10 + 15O2 → 10CO2 + 10H2O [1] accept: multiples including fractions allow: ecf for correct equation from any incorrect alkene




8 (a) proton donor; [1] (b) equal concentrations of both (solutions); [1]

add Universal indicator / determine pH / pH paper; [1] ethylamine has lower pH / ORA; [1] or equal concentration of both (solutions); [1] measure conductivity of aqueous ethylamine and sodium hydroxide; [1] ethylamine will have lower conductivity / sodium hydroxide will have higher conductivity; [1]

(c) add strong(er) base / NaOH / KOH; [1]

warm / heat; [1] (d) (ethylamine forms) hydroxide ions / OH– (in water); [1]

hydroxide ions / OH– reacts with iron(III) ions / Fe3+; or iron(III) hydroxide / Fe(OH)3 (forms as a brown precipitate); [1]

note: balanced or unbalanced ionic equation i.e. Fe3+ + (3)OH– → Fe(OH)3 scores both marks

CAMBRIDGE INTERNATIONAL EXAMINATIONS


MARK SCHEME for the October/November 2012 series

0620 CHEMISTRY



Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2012 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.


Mark Scheme Syllabus Paper


© Cambridge International Examinations 2012

1 (a) diffusion or fractional distillation; (b) fractional distillation; (c) simple distillation; (d) crystallisation; (e) filtration;

(f) chromatography;

[Total: 6] 2 (a) (i) become darker; [1] (ii) increase; [1] (iii) black / dark grey; [1] not: brown solid; [1] (b) (i) same Z / same number of protons; [1] accept: atoms of the same element different number of neutrons / different nucleon number / different mass

number; [1] (ii) 53 protons and 53 electrons; [1] 78

neutrons; [1] (iii) xenon; [1] (c) BrF3 / F3Br; [1] BrF5 / F5Br; [1]

[Total: 11]




3 (a) (i) any three from: particles have more energy; move faster; collide more frequently; more successful collisions; [3] accept: atoms or molecules for particles not: electrons not: vibrate more (ii) reaction faster with temperature increase; [1] enzymes denatured / destroyed; not: killed [1] (b) (i) bigger initial gradient; [1] same final volume of nitrogen; [1] (ii) decrease / slows down; [1] (iii) concentration of organic compound decreases; [2] compound used up = [1] or: fewer particles; collision rate decreases; (c) (i) carbon monoxide-incomplete combustion; [1] carbon - containing fuel / fossil fuel / petrol; [1] oxides of nitrogen - oxygen and nitrogen react; [1] at high temperature / in engine; [1] not: in exhaust (ii) carbon monoxide to carbon dioxide; [1] oxides of nitrogen to nitrogen; [1] correct balanced equation; [1] [Total: 17]




4 (a) giant covalent; [1] or: polymer made from monomers; (b) (i) any three from: high mp / bp; hard; brittle; insoluble (in water); poor conductor of electricity / heat; [3] (ii) carbon / diamond / silicon / boron; [1] not: graphite (c) (i) sodium hydroxide / any named alkali / reactive metal; [1] (ii) named acid; [1] zirconium oxide; [1] [Total: 8] 5 (a) (i) rate of reaction; [1] influenced by light / only happens in light; [1] or: turns light into chemical energy = [2] accept: light is catalyst = [1] (ii) reduction of silver halides; [1] they are reduced to silver / 2AgCl → 2Ag + Cl2; [1] appropriate importance given; [1] or: photosynthesis; correct comment about chemistry carbon dioxide to carbohydrates / carbon

dioxide to oxygen; anything sensible e.g. its role in the food chain or decrease greenhouse

effect or oxygen for respiration; or: chlorination; making chloroalkanes; appropriate importance given; (b) (i) pressure would move position of equilibrium to right / increase yield of COCl2; [1] increase pressure favours side with less (gas) molecules / smaller volume; [1] (ii) increase temperature favours endothermic reaction; [1] so less products / reduce yield; [1] (iii) keeps rate high / increase rate at lower temperatures; [1]




(c) each chlorine 1 bp and 3 nbps; [1] 4 e between carbon atom and oxygen atom; [1] 2 nbps on oxygen atom; [1] [Total: 13] 6 (a) (i) amino acid / peptides; [1] salt / carboxylate or soap / fatty acid or glycerine / alcohol; [1] sugars or glucose; [1] accept: named sugar (ii) polyester; [1] allow: named polyester polyamide; [1] allow: nylon (b) one correct amide linkage; [1] second amide linkage correctly orientated – NHCO – followed by – NHCO –; [1] note: monomers are amino acids not diamines or dicarboxylic acid (c) bromine / bromine water / aqueous bromine; [1] unsaturated - brown / orange to colourless not: clear [1] saturated - stays brown / orange [1] or: alkaline potassium manganate(VII); from purple / pink to green / brown; stays purple; or: acidic potassium manganate(VII) from purple / pink to colourless; not: clear stays purple; [Total: 10] 7 (a) (i) melting point is below 25°C; [1] boiling point above 25°C; [1] accept: argument based on actual values note: 25°C is between mp and bp = [2] (ii) strontium loses 2e; [1] sulfur gains 2e; [1] (iii) hydrogen chloride / hydrochloric acid; [1] accept: sulfurous acid or sulfur dioxide (iv) molten strontium chloride has ions / ionic compound; [1] which can move; [1] sulfur chloride has no ions / only molecules / molecular / covalent; [1]




(b) (i) strontium carbonate does not dissolve / no effervescence; [1] note: not just reaction is complete (ii) to remove excess / unreacted / undissolved strontium carbonate; [1] (iii) water of crystallisation needed / 6H2O in crystals / would get anhydrous salt /

would not get hydrated salt / crystals dehydrate; [1] not: just to obtain crystals (c) number of moles of HCl used = 0.05 × 2 = 0.1 [1]

number of moles of SrCl2.6 H2O which could be formed. = 0.05 [1] mass of one mole of SrCl2.6H2O is 267 g theoretical yield of SrCl2.6H2O = 0.05 × 267 = 13.35 g [1] percentage yield = 6.4 / 13.35 × 100 = 47.9% [1] accept: 48% allow: ecf [Total: 15]




0620 CHEMISTRY








1 (a) (i) Sb; (ii) Xe / B;

(iii) Sr / Te / A / D;

(iv) Sn and I / E and F; (v) Sr / A; [5] (b) any two from: physical niobium is harder; stronger; higher mp/bp; higher density [2] note: there has to be a comparison any two from: chemical niobium is less reactive; forms coloured compounds; forms complex ions; its

compounds have catalytic properties; has more than one oxidation state; has more than one valency electron; [2]

note: the response has to refer to or compare properties of both elements

[Total: 9] 2 (a) liquid; [1] (b) (l) and (s); [1] reversible sign; [1] accept: X in equation ignore: any compounds just look for state symbols must be the same compound on both sides of equation (c) boiling / condensation; [1] accept: evaporation or vaporisation (d) (in region BC) solid melts / liquid boils (in region DE); [1] at one / fixed / sharp / single / specific temperature; [1] [Total: 6] 3 (a) (i) correct structure of an isomer e.g. 2-chloropropane; [1] (ii) chlorine; [1] light / heat / lead tetraethyl; [1]




(iii) could produce 2-chloropropane; [1] could produce HCl; [1] or could produce dichloropropanes = [2] (b) (i) add silver nitrate / lead nitrate; [1] yellow precipitate; [1] note: do not insist on presence of dilute nitric acid

(ii) propanol / propan-1-ol; [1]

(c) (i) for A; reaction slower; decreased collision rate; less bromobutane present / concentration of bromobutane less / less reacting

particles; [2] any two accept: reverse arguments for B

(ii) halogens Cl > Br > I reactivity / reactivity decreases down group; [1]

organic halides I > Br > Cl / reactivity increases down group; [1] opposite without explanation = [1] (iii) any three from: less energy; particles move slower; less collisions / fewer particles have energy to react / fewer successful collisions; slower rate; [3] [Total: 15] 4 (a) C + O2 → CO2 [1] (b) (i) CO2 already formed (from C burning or from CaCO3); [1] then carbon reacts with carbon dioxide; [1] or C + CO2 → 2CO = [2] If equation not balanced = [1] (ii) Fe2O3 + 3CO → 2Fe + 3CO2 [2] not balanced = [1] not: reduction by carbon (c) to remove / neutralise silica / silicon dioxide / silicon(IV) oxide / sand; [1] reacts with limestone to form slag / calcium silicate; [1] CaCO3 + SiO2 → CaSiO3 + CO2 [1] or CaO + SiO2 →CaSiO3

or CaCO3 → CaO + CO2




(d) (i) galvanising / galvanisation / sacrificial protection; [1] (ii) sacrificial protection / zinc is sacrificed; zinc corrodes rather than iron; zinc is oxidised in preference to iron; zinc reacts with oxygen and / water in preference to iron; zinc more reactive / electropositive than iron; zinc loses electrons more readily than iron; electrons move on to iron any three [3]

[Total: 12]

5 (a) any two from: bleaching (wood pulp / silk / straw); manufacture of sulfuric acid / SO3 / in Contact process; fumigating / sterilising; refrigerant; making dyes; making wine; insecticide;

fungicide; [2] (b) burn / heat / react sulfur; [1] in air / oxygen; [1] or burn / heat / roast zinc sulfide or lead sulfide; in air / oxygen; (c) from purple / pink; not: red [1] to colourless; not clear [1]

(d) number of moles of Na2SO3 = 3.15/126 = 0.025 [1] number of moles of SO2 formed = 0.025 [1] volume of SO2 = 0.025 x 24 = 0.6 dm3/litres or 600 cm3 [1] allow: ecf for 1.6 g of SO2 [1] only If used 22.4 max [2] note: need correct units for last mark [Total: 9]




6 (a) (i) correct arrow from negative terminal of battery or from anode; [1] (ii) from battery / power supply / cell; [1] from negative electrode of battery to external circuit; [1] or from anode; from iodide ion losing electron or oxidation of anion; (iii) ions cannot move in solid / ions can move in liquid; [1] (b) copper; [1] (changes to) sulfuric acid; [1]

hydrogen; [1] (changes to) potassium hydroxide; [1]

(c) (i) 2H+ + 2e � H2 [2] not balanced = [1] (ii) 4OH- � O2 + 2H2O + 4e [1] (iii) water used up; [1] (d) it is a cell; [1] hydrogen reacts with oxygen; [1] this reaction produces energy / is exothermic / produces flow of electrons /

changes chemical energy to electrical energy; [1]

[Total: 15] 7 (a) (i) CnH2n+1OH [1] (ii) 116-17 = 99, 2n+1 = 99, n = 7 for any evidence of working out [1] C7H15OH [1] (iii) 4bps around C; [1] 1 bp on each hydrogen; [1] 2bps and 2nbps on oxygen; [1] (b) (i) increases yield / moves equilibrium to RHS / favours forward reaction; [1] high pressure favours side with smaller number of (gas) molecules; [1]

(ii) any two from: higher temperature / catalyst causes faster reaction; comment about compromise conditions to give best rate and yield;

at 250oC (lower temp) higher yield / forward reaction favoured; at 350oC (higher temp) lower yield / back reaction favoured; [3]




(c) (i) methanoic acid; [1] correct SF showing all bonds; [1] accept: -OH (ii) methyl methanoate; [1] [Total: 14]




0620 CHEMISTRY








1 (a) Ca / calcium; [1] (b) Kr / krypton; [1] (c) Ge / germanium; [1] (d) Ni / nickel or Cr / chromium; [1] (e) Br / bromine / Br2; [1] (f) Se / selenium; [1] (g) Cu / copper; [1] (h) Br / bromine / Br2; [1] [Total: 8] 2 (a) (i) manufacture of plastics / (solvents for) dry cleaning / metal degreasing / textiles

/ agrochemicals / pharmaceuticals / insecticides / dyestuffs / household cleaning products / bleach / water treatment / swimming pools / kill bacteria or germs or microorganisms or pathogens / sterilisation / disinfectants; [1]

(ii) electric light bulbs / fluorescent tubes / (inert gas shield for) arc welding /

production of titanium / inert atmosphere / car headlights / food packaging; [1] (iii) (manufacture of) polyethene / polyvinyl chloride (PVC) / making polymers / (to

prepare) epoxyethane (which is used in the manufacture of detergents / (to make) ethylene glycol (which is used to prepare Terylene) / (to make) anti-freeze / or making ethanol (accept making alcohol) / ripening fruits; [1]

(iv) (making) steel / (oxy-acetylene) welding / cutting of metals / medical or diving or

(oxygen tanks in) hospitals / astronauts / (deep sea) diving / fire fighters; [1]

(b) liquid air; [1] fractional distillation; [1]

[Total: 6]




3 (a) explanation of evaporation e.g. particles (or molecules) with a lot of energy leave the liquid / bromine particles break free from each other / forces or bonds between bromine molecules broken / molecules (in liquid) have weak forces holding them together / weak intermolecular forces / Van der Waals forces between molecules (don’t have to be stated as weak) / (weak intermolecular forces alone scores this mark);

allow: particles (or molecules) of bromine escape from liquid [1] diffusion / diffuse / movement of particles; [1]

explanation of diffusion involving qualified movement of molecules / particles i.e. random movement of molecules / particles move in all directions; [1]

(b) air more dense / heavier / higher Mr than hydrogen; [1] hydrogen diffuses faster (than air diffuses out); [1] accept: diffusion in is faster than out (without naming gases) pressure inside pot is greater (than outside); [1] air less dense / lighter / lower Mr than carbon dioxide; [1] air diffuses / moves faster (than carbon dioxide); [1] accept: diffusion out is faster than in (without naming gases) pressure inside pot less (than outside); [1] ORA in both parts

[Total: 9] 4 (a) (i) zinc mixed with an element(s) or metal(s) or non-metal; [1] (ii) galvanising / baths / coating steel (i.e. description of galvanising) / roofing /

sacrificial protection / protection from rusting / electroplating / zinc plating / batteries; [1]

(iii) (lattice) positive ions / cations / metal ions / sea of electrons / delocalised or free

or mobile or moving electrons; [1] attraction between positive ions and electrons; [1] the layers (of ions) or particles can slide or slip or shift past each other; [1] (iv) different atom / ion / particle of different size; [1] prevents (layers / atoms / ions / particles / molecules) moving / slipping /

sliding / shifting; [1] (b) (i) heat with carbon or coke or carbon monoxide; [1] (ii) ZnO + H2SO4 � ZnSO4 + H2O [2] [1] for correct reactants [1]for correct products




(iii) zinc (not: ions) more reactive than silver and lead; [1] zinc displaces both metals / silver and lead produced / ions become atoms / zinc

reduces silver ions and lead ions; [1] (silver and lead) can be removed by filtering / centrifugation / decanting; [1]

an ionic equation; i.e. Zn + 2 Ag+ � Zn2+ + 2Ag or Zn + Pb2+ � Zn2+ + Pb [1] allow: any two correct half equations

(iv) cathode labelled carbon / zinc / platinum; [1] zinc deposited at cathode; [1] oxygen formed (at anode); [1] (electrolyte becomes) sulfuric acid / remaining solution contains H+ and SO4

2-; [1] [Total: 18] 5 (a) (i) add bromine water / bromine / aqueous bromine; [1] colourless; [1]

or add potassium manganate(VII) / permanganate; (ignore acid or alkali) [1] colourless; [1] (ii) add metal / carbonate / insoluble base / strong alkali allow: ammonia with an

indicator / use pH meter; [1] COND: on reagent

metal - hydrogen given off / metal dissolves / effervescence / gas given off / burning splint pops; carbonate - carbon dioxide given off / effervescence / gas given off / limewater milky; insoluble base - solution formed / dissolves; alkali - use of indicator to show neutralisation / temperature increase; pH meter - gives pH less than 7 [1]

(b) ethyl propenoate; [1] correct SF all bonds shown;; [2] allow: [1] for correct displayed ester linkage




(c) (i) number of atoms of each element; [1] in one molecule; [1] (ii) 2; [1] (iii) C=C [1]

(iv) HOOC(CH3)C=C(CH3)COOH [Total: 12]

6 (a) (i) Zn + 2HCl � ZnCl2 + H2 [2] not balanced = [1] (ii) 3 bps and 1 nbp around As; [1] 1 bp each hydrogen atom; [1] (b) (i) (97.4 / 75 =) 1.3 and (2.6 / 1 = ) 2.6; [1] empirical formula AsH2; [1] note: correct formula with no working = [1] (ii) As2H4; [1] (iii) H2As–AsH2 / AsH2–AsH2; [1] (c) (i) amide / peptide; [1] (ii) named strong acid / alkali; [1] allow: HCl / enzymes (iii) amino acid; [1] allow: peptides (d) (i) Cu and As have more than one oxidation state / valency; [1] (ii) 3Cu2+ + 2AsO4

3- � Cu3(AsO4)2 [2] either side correct = [1] [Total: 14]




7 (a) (making) fertilisers / nitric acid / nylon / refrigeration / explosives / cleaning products; [1] (b) alkane / named alkane; [1] water / steam; [1] heat / catalyst; [1] or electrolysis; [1] suggest suitable electrolyte; (allow: water) [1] hydrogen at cathode; [1] or cracking; [1] alkane / named alkane; [1] heat or catalyst [1] (c) any five from: faster; (rate) [1]

more collisions / molecules closer together / more particles per unit volume; [1] (collisions) more frequent / more often / more chance / more effective or successful collisions / more collisions with Ea / increase rate of collisions; [1] higher yield / moves (equilibrium) to RHS / more ammonia / to side of products / high pressure favours the reaction with less moles; [1] less moles / molecules / volume on RHS ORA (can be implied in previous comments) [1] high pressure means lower temperature can be used to achieve comparable rate (thus saving energy); [1]

7 (d) (i) endothermic takes in / absorbs / uses / needs / gains energy / heat and

exothermic gives out / loses energy / heat; [1] (ii) 2328 (ignore + or – ) / 6 × 388 (not evaluated); [1] 944 + 1308 / 2252 and endothermic and exothermic in table; [1] 2328>2252 or (–) 76 kJ; [1] or energy of products / RHS > reactants / LHS or energy needed to break bonds < energy given out on formation of bonds. [Total: 13]



MARK SCHEME for the May/June 2013 series

0620 CHEMISTRY


This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.





1 (a) (i) contains carbon and hydrogen [1] cond: only / just [1]

(ii) (different) boiling points [1]

cond: separate [1] (b) bitumen-making roads / roofs / water-proofing, etc. [1]

lubricating fraction – waxes / vaseline / grease, etc. or machinery example, e.g. (oil a) bike / hinges / reducing friction [1]

paraffin fraction – jet fuel / (home) heating or tractors or cooking or lighting [1]

gasoline fraction – petrol or fuel for cars / vans / trucks [1] [Total: 8]

2 (a) 3 or III [1]

(b) good conductor and it is a metal/has delocalised (free) electrons [1]

(c) N or P or As or Sb [1] accept Bi

(d) M2(SO4)3 [1] accept: Ga2(SO4)3

(e) it would react with/dissolves in a named strong acid [1] it would react with/dissolves in a named alkali [1] it shows both basic and acid properties =1 [1] it reacts with both acids and bases/alkalis =1 [1] [max 2]

[Total: 6]




3 (a) (i) pieces have (same) surface area [1] same amount / mass / quantity / volume / number of moles of carbonate [1]

(ii) no more bubbles / carbon dioxide or piece disappears / dissolves [1]

(b) experiment 1 Ca2+ + CO2 + H2O [1]

(c) (i) more concentrated or higher concentration (of acid) (in experiment 1) [1] accept: arguments based on collision theory

(ii) ethanoic acid is a weak acid or hydrochloric acid is a strong acid [1] accept: stronger or weaker

ethanoic acid less ionised / dissociated / lower / smaller concentration of hydrogen ions [1] accept: less hydrogen ions and vice versa argument but not dissociation of ions

(iii) lower temperature (particles) have less energy [1]

moving more slowly [1] fewer collisions / lower collision rate [1] or lower temperature (particles) have less energy [1] fewer particles collide [1] with the necessary energy to react [1] note: less energy fewer successful collisions gains all 3 marks

[Total: 10] 4 (a) it is an alkane or hydrocarbon [1]

it is saturated or only C—C single bonds [1] accept: no double bonds

(b) molecular formula C6H12 [1] empirical formula CH2 [1]

(c) correct structural formula of cyclobutane [1]




(d) (i) C6H12 [1] accept: a correct structural formula

(ii) same molecular formula not: chemical formula [1]

different structural formulae / structures [1]

(e) add bromine (water) or (l) [1] cond: (remains) brown or orange or red or yellow [1] cond: changes from brown, etc. to colourless or decolourises [1] not: clear OR potassium manganate(VII) [1] note: oxidation state not essential but if given must be correct or [0] accept: potassium permanganate cond: remains pink / purple [1] cond: changes from pink to colourless (acidic) [1] not: clear cond: change from pink to green / brown (alkaline)

[Total: 11] 5 (a) (i) any metal above zinc

Mg → Mg2+ + 2e– [1]

(ii) Zn + 2Ag+ → Zn2+ + 2Ag [2] Note: not balanced only [1]

(iii) because they can accept or gain electrons / change into atoms or can be reduced [1]

(iv) Ag+ or silver [1]

charge not essential but if given must be correct

(v) Ag+ and Cu2+ or silver and copper [1] charge not essential but if given must be correct




(b) Cu Sn Cd Zn (i.e. all 4 in correct order) [1] relates order to voltage [1]

one relevant comment from: [1] higher reactivity metals are the negative electrode / copper is least reactive because it is the positive electrode because copper would have the lowest voltage / copper cell V = 0 / the bigger the difference in reactivity, the bigger the voltage / zinc has highest voltage because it is most reactive / more reactive metals have higher voltage

[Total: 9] 6 (a) (i) proton or H+ acceptor [1] (ii) (measure) pH or (use) UI indicator [1]

note: can be implied need not be explicit sodium hydroxide has higher pH / ammonia(aq) has lower pH [1] (this sentence would score 2 marks) or appropriate colours with UI / appropriate numerical values [1] ammonia is closer to green, blue-green, turquoise or lighter blue sodium hydroxide is darker blue / purple / violet [1] or measure electrical conductivity [1] can be implied need not be explicit ammonia (aq) is the poorer conductor/ sodium hydroxide is the better conductor [1]




(b) any five from:

• high pressure favours lower volume side / movement to right / ammonia side, or high pressure increases the yield

• high pressure increases rate

• low temperature favours exothermic reaction / increases yield / favours the forward reaction

• low temperature gives low rate or vice versa

• catalyst increases rate or lowers activation energy

• 450 °C low enough to give an economic yield but with catalyst gives a fast enough rate note need whole concept to get this compromise temperature point [5]

(c) 2NH3 + NaClO → N2H4 + NaCl + H2O [2] not balanced only 1

(d) 4 hydrogen atoms 1 bonding pair each [1] 2 nitrogen atoms with 1 bonding pair between them [1] one non-bonding pair on each N (need not be seen as a pair) [1]

(e) (i) pH increases [1]

(ii) oxygen needed for rusting / removes oxygen / reacts with oxygen [1] [Total: 15] 7 (a) (i) add carbon / animal charcoal [1]

filter [1]

OR repeat experiment without indicator [1] using same quantity / volume of acid [1]

(ii) add magnesium metal / carbonate / oxide / hydroxide

to (hot) (hydrochloric) acid [1]

cond: until in excess or no more dissolves or reacts [1]

cond: filter (to remove unreacted solid) [1]




(b) number of moles of HCl = 0.020 x 2.20 = 0.044 [1] number of moles of LiOH = 0.044 concentration of LiOH = 0.044/0.025 = 1.769 (mol / dm3) [1] accept 1.75 to 1.77 need 2 dp correct answer scores = 2

(c) (for LiCl.2H2O) mass of one mole = 78.5 [1] percentage water = 36 / 78.5 x 100 [1] 45.9 so is LiCl.2H2O [1] only award the marks if you can follow the reasoning and it gives 45.9% of water note: if correct option given mark this and ignore the rest of the response allow: max 2 for applying a correct method to another hydrate, [1] for the method and [1] for the correct value, working essential

[Total: 10] 8 (a) (i) regular arrangement / repeating pattern NOT structure [1]

cond: ions [1] not molecules / atoms

(ii) attraction between opposite charges / electrostatic attraction [1]

(b) delocalised / mobile / free / sea of electrons [1] positive ions / cations not atoms / protons / nuclei [1] attraction between these electrons and ions [1]

(c) giant covalent

no ions [1] no delocalised / free / mobile / sea of electrons or all electrons [1]

ionic in ionic solid ions cannot move [1] liquid ionic compound ions can move [1]

metallic (both solid and liquid) metals have delocalised (or alternative term) electrons [1] [Total: 11]




0620 CHEMISTRY







1 (a) (i) named noble gas [1] accept: any noble gas accept: symbol

(ii) H2O / CO2 [1]

not: names not: equations

(b) (i) oxygen and nitrogen (in air) (react) [1] at high temperature [1] accept: in engines / lightning not: in exhausts

(ii) fossil fuels / fuels which contain sulfur [1]

accept: named fossil fuel such as coal / oil / natural gas burn / combust [1]

(iii) any two from:

damage buildings / soil acidification / leaching from soil / soil nutrients become unavailable / kill microbes / acidify lakes / kill fish / damage trees / reduction in plant growth / crop loss [2]

(c) (i) oxygen reacts with copper [1] to form copper oxide (which is black) [1]

(ii) measure volume at room temperature / gas has different volumes at different

temperatures / volume of gas depends on temperature / hot gas has higher volume / heat causes expansion (of gases) / ORA [1]

(iii) no oxygen left or all the oxygen has reacted (with copper) [1] (iv) 39–40 cm3 note: units required [1]

2 (a) B 3919

K [1]

positive charge + [1]

C 6530

Zn [1]

D 168O [1]

charge 2– [1]

E 7031

Ga [1]

(b) number of p = number of e [1]

number of p > number of e [1]

number of p < number of e [1]




3 (a) (i) complete combustion / combustion in excess oxygen [1]

of fuels containing carbon / fossil fuels / hydrocarbon (fuels) [1]

produce carbon dioxide / increase percentage of CO2 in atmosphere [1]

(ii) living things / cells / plants / animals / humans / micro-organisms [1] (oxidise / react with) oxygen and food / foodstuff / named foodstuff / carbohydrate / sugar / glucose [1] produces carbon dioxide [1]

(b) (i) glucose or starch or carbohydrate [1] oxygen [1]

(ii) light / sunlight / sun / UV [1]

chlorophyll accept: chloroplast [1]

4 (a) (i) first reaction

volume / moles / molecules of reactants and products are different [1]

second reaction volume / moles / molecules of reactants and products are the same [1]

(ii) first reaction (forward) reaction is endothermic [1]

second reaction (forward) reaction is exothermic [1]

(b) (i) C8H18 → 2C4H8 + H2 [1]

(ii) 2H+ + 2e → H2 [2] or 2H3O

+ + 2e → H2 + 2H2O accept: –2e on right hand side accept: e– note: not balanced = 1

(iii) chlorine / Cl2 / [1]

cond: water treatment / solvents / plastics / PVC / bleach / disinfectants / HCl / kill bacteria / sterilising water / chlorination of water / swimming pools / pesticides / herbicides / insecticides / germicides / pharmaceuticals [1]

sodium hydroxide/NaOH [1] cond: making soap / degreasing / making paper / detergents / bio-diesel / paint stripper / clearing drains / alumina from bauxite / oven cleaner / bleach [1]




5 (a) (i) does not decay or non-biodegradable or flexible or bendable or easily moulded or low density / light / lightweight or waterproof / insoluble in water or does not corrode or durable [1]

(ii) any two from: [2]

chlorine hydrogen chloride carbon monoxide

(b) (i) CH3—CH = CH2 [1] note: can be fully or semi-displayed, C = C must be shown

(ii) correct repeat unit [1]

–CH(C6H5)–CH2–

continuation shown [1]

(c) glucose two products (polymer and water) / condensation (polymerisation) / (small) molecules removed [1]

phenylethene one product (polymer) / addition (polymerisation) [1]

6 (a) (i) ions cannot move / no free ions in solid state [1]

ions can move / free ions in liquid state [1] note: ions can only move in liquid state = 2

(ii) reduce melting point / reduce energy costs / better conductor when dissolved in cryolite [1]

(iii) burns in oxygen / reacts with oxygen / oxidised by oxygen / forms carbon dioxide / forms

carbon monoxide [1]

(iv) high melting point / inert / unreactive [1]

(b) protective / unreactive / resists / prevents corrosion / non-porous (layer) [1]

of (aluminium) oxide [1]

(c) (i) good conductor (of electricity) [1] low density / light / lightweight [1]

(ii) steel core (increased) strength / prevent sagging / to increase separation of pylons / support [1]




7 (a) (i) CH3COOCH2CH3 / CH3CO2CH2CH3 / CH3COOC2H5 / CH3CO2C2H5 / C2H5OOCCH3 / CH3CH2OOCCH3 not: –OCO– linkage [1] note: formulae can be displayed or semi-displayed note: penalise sticks (i.e. any missing atoms)

(ii) butyl methanoate [1]

(b) (i) fats / vegetable oils / triglycerides / lipids [1]

(ii) two correct ester linkages, e.g. –OOC / –O2C and –COO / –CO2 [1]

contents of the ‘boxes’ being C6H4 and C2H4 or CH2CH2 [1] continuation bonds at both ends [1]

(c) (i) to make colourless / invisible (spots) [1]

visible / coloured / seen / position made clear / indicate [1]

(ii) distance travelled by sample = Rf [1] distance travelled by solvent (front)

(iii) sample 1 Rf = 0.20 to 0.24 tartaric (acid) [1]

sample 2 Rf = 0.44 to 0.48 malic (acid) [1] 8 (a) (i) (the number of particles which is equal to the number of atoms in) 12 g of carbon 12

or the mass in grams which contains the Avogadro’s constant number of particles or

Avogadro’s constant or 6 to 6.023 × 1023 of atoms / ions / molecules / electrons / particles or (the amount of substance which has a mass equal to) its relative formula mass / relative atomic mass / relative molecular mass in grams or (the amount of substance which has a volume equal to) 24 dm3 of a gas at RTP [1]

(ii) (Avogadro’s constant is the) number of particles / atoms / ions / molecules in one mole of a substance or the number of carbon atoms in 12 g of C(12). or the number of particles / molecules in 24 dm3of a gas at RTP or

6 to 6.023 × 1023 (particles / atoms / ions / molecules / electrons) [1]

(b) CH4 and SO2 [1]

2/16 = 1/8 or 0.125 moles of CH4 AND 8/64 = 1/8 or 0.125 moles of SO2 [1]




(c) (i) 4.8/40 = 0.12 moles of Ca 3.6/18 = 0.2 moles of H2O both correct [1]

(ii) Ca is in excess (no mark) (because 0.12 moles of Ca need) 0.24 moles / 4.32 g of H2O

to react [1] there is not enough / there are 0.2 moles / 3.6 g of H2O [1] or Ca is in excess (no mark) (because 0.2 moles / 3.6 g of water will react with) 0.1moles/4.0 g of Ca [1] there is more than that / there are 0.12 moles / 4.8 g of Ca [1] or Ca is in excess (no mark) because the mole ratio Ca:H2O is 3:5 / mass ratio 4:3 [1] which is bigger than the required mole ratio of 1:2 / mass ratio 10:9 [1] or Ca is in excess (no mark) because the mole ratio H2O:Ca is 5:3 / mass ratio 3:4 [1] which is smaller than the required mole ratio of 2:1 / mass ratio 9:10 [1]

(iii) 0.02 × 40 = 0.8 (g) [1]




0620 CHEMISTRY







1 (a) (i) element cannot be broken into anything simpler [1] by chemical means [1] OR made up of one type of atom only [2]

(ii) compound two or more different elements [1] chemically bonded together [1] (iii) mixture

two or more substances not chemically joined together [1]

(b) (i) mixture [1] (ii) compound [1] (iii) element [1] (c) conductivity (of heat or electricity) [1] [Total: 9] 2 (a) (i) large / high surface area [1] high collision rate / collide more / many collisions [1] (between oxygen molecules and aluminium atoms) NOT faster collisions

(ii) concentration [1] of reactants decreases [1] allow one mark ONLY for: for reactants used up or amount of reactant decreases (iii) any three of four from one strand:

M1 increase in temperature

M2 molecules move faster or particles have more energy

M3 higher collision rate

M4 more successful collisions or more particles have enough energy to react/Ea

[3] (b) (i) flour or wood dust or coal dust or carbon or sugar [1]




(ii) any three from: powder and larger pieces / different sized particles use suitable named solid, e.g. magnesium suitable named solution, e.g. named acid or copper sulfate(aq) result – powder reacts faster than larger pieces [3] NOT Cu (with acid); K / Na with anything 3 (a) (i) cars, ships, bridges, construction, white goods, screws, nails, roofing, fencing, etc. [1]

(ii) e.g. stainless steel [1] cooking utensils, surgical equipment, sinks or main use [1] (b) blow in oxygen NOT air [1] carbon dioxide and sulfur dioxide (escape as gases) [1] COND on reaction with air / oxygen add calcium oxide / quicklime [1] ALLOW calcium carbonate, limestone phosphorus oxide or silicon oxide (are acidic) reacts (with calcium oxide / CaCO3) [1] to form slag / calcium silicate [1] 4 (a) (i) any ambiguous formula, e.g. GeH3-GeH2-GeH3 [1] (ii) GenH2n+2 [1] NOT C instead of Ge (b) correct formula COND 4bps around germanium atom [1] COND 3nbps and 1bp around each chlorine atom [1] (c) four oxygen atoms around each germanium atom [1] two germanium atoms around each oxygen atom [1] tetrahedral [1] (d) oxidation [1] COND increase in oxidation number [1] ACCEPT: electron loss




5 (a) (i) any Group 1 metal [1] ACCEPT: lithium

(ii) 2Pb(NO3)2 → 2PbO + 4NO2 + O2 [2] PbO [1] COND balancing [1] (iii) the metal in a (i) is more reactive than lead [1] more reactive metals have more stable compounds OR has stronger (ionic) bonding [1] (b) (i) speed / rate of forward reaction = speed / rate of back reaction [1] OR macroscopic properties do not change / constant (with time) (ii) goes darker OR goes brown [1] COND lower pressure favours side with more moles [1] COND this is NO2 side OR reactant side OR goes left [1] (iii) exothermic [1]

low temperatures favour the exothermic reaction or low temperatures moves equilibrium to right / product side / towards N2O4 [1]

(iv) forward reaction is bond forming [1] 6 (a) (i) measure melting point NOT just heating [1]

pure sample would melt at 135 °C [1]

OR impure would melt lower than 135 °C (ii) C3H4O4 [1] (iii) C2H4O2 OR CH3COOH [1] ethanoic OR acetic acid [1] both marks are independent of each other (iv) ester NOT organic, covalent [1] (b) (i) malonic is a weaker acid/less dissociated OR sulfuric acid is a stronger acid/more dissociated [1] NOT sulfuric acid is a strong acid




(ii) add piece of suitable metal, e.g. Mg ALLOW Al, Ca NOT K, Na, Cu [1] sulfuric acid reacts faster OR malonic reacts slower [1] OR as above add a piece of CaCO3, if soluble carbonate then [1] only OR measure electrical conductivity [1] sulfuric acid is the better conductor OR malonic acid poorer conductor [1] NOT sulfuric acid is a good conductor (c) (i) sodium malonate and water [1] (ii) CuSO4

H2O [2] (iii) CH2(COO)2 Mg

H2 [2] (iv) K2SO4 CO2 and H2O NOT H2CO3 [2] [Total: 16] 7 (a) (i) a compound which contains carbon and hydrogen only [1] (ii) alkanes contain only C-C single bonds or they are saturated (hydrocarbons) or have the general formula CnH2n+2 [1] alkenes contain at least one C=C double bond or they are unsaturated (hydrocarbons) or have the general formula CnH2n [1]

(b) C20H42 → 2C4H8 + 2C2H4 + C8H18 [1] (c) (i) any unambiguous structure of BrCH2CH2Br [1] NOT just C2H4Br2

(ii) CH3-CH=CH-CH3 [2] For any butene [1] only

(iii) (CH3-CH2-CH=CH2) + H2O [1] → CH3-CH2-CH2-CH2OH [1] [2] ALLOW CH3-CHOH-CH2-CH3 butene reacts with water/steam (to form butanol) ONLY [1]

(iv) C6H12 + H2 → C6H14 [2] alkenes react with hydrogen [1] ONLY (d) volume of oxygen used = 150 cm3 [1]




volume of carbon dioxide formed = 100 cm3 [1] any equation of the combustion of an alkene e.g. 2C5H10 + 15O2 � 10CO2 + 10H2O formulae [1] COND balancing [1]




0620 CHEMISTRY


This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.





1 (a) uranium / plutonium / thorium [1] (b) graphite / carbon [1] (c) platinum / titanium / mercury / gold [1] NOT: carbon / graphite (d) helium [1] (e) nitrogen / phosphorus [1] (f) argon [1] ACCEPT: any ion 2 + 8 + 8 e.g. K+ etc. (g) tellurium [1] ACCEPT: correct symbol [Total: 7] 2 (a) Any three of: iron is harder iron has higher density ACCEPT: heavier or potassium lighter iron has higher mp or bp iron has higher tensile strength or stronger iron has magnetic properties [3] NOTE: has to be comparison, e.g. iron is hard (0) but iron is harder (1) NOT: appearance e.g. shiny ACCEPT: comparative statements relating to potassium (b) potassium hydrogen (1) and potassium hydroxide (1) zinc hydrogen (1) and zinc oxide (1) copper no reaction (1) [5] [Total: 8]




3 (a) (i) fractional distillation [1] (liquid) air [1] (ii) cracking / heat in presence of catalyst [1] of alkane / petroleum [1] to give an alkene and hydrogen [1]

OR: electrolysis (1) named electrolyte (1) hydrogen at cathode (1)

OR: from methane (1) react water / steam (1) heat catalyst (1) only ACCEPT: water with methane or electrolysis (b) (i) the pair with both graphs correct is C [1] NOTE: mark (b)(ii) independent of (b)(i) (ii) high pressure favours side with lower volume / fewer moles [1] this is RHS / product / ammonia [1] %NH3 / yield increases as pressure increases [1] the forward reaction is exothermic [1] exothermic reactions favoured by low temperatures [1] %NH3 / yield decreases as temperature increases [1] ACCEPT: reverse arguments (iii) increases reaction rate [1] ACCEPT: reduces activation energy [1] OR: decreases the amount of energy particles need to react OR: economic rate at lower temperature so higher yield [Total: 14] 4 (a) (i) (mass at t =0) – (mass at t = 5) [1] NOTE: must have mass at t = 5 not final mass (ii) fastest at origin slowing down between origin and flat section gradient = 0 where gradrient = 0 three of above in approximately the correct positions [2] (iii) 3 correct comments about gradient = [2] 2 correct comments about gradient = [1] 1 correct comment about gradient = [0] [2] (b) start at origin and smaller gradient [1] same final mass just approximate rather than exact [1]




(c) (i) smaller surface area [1] lower collision rate [1] (ii) molecules have more energy [1] collide more frequently / more molecules have enough energy to react [1] (d) number of moles of HCl in 40 cm3 of hydrochloric acid, concentration 2.0 mol / dm3 = 0.04 × 2.0 = 0.08 [1] maximum number of moles of CO2 formed = 0.04 [1] mass of one mole of CO2 = 44 g [1] maximum mass of CO2 lost = 0.04 × 44 = 1.76 g [1] [Total: 15] 5 (a) (i) have same molecular formula / both are C5H12 [1]

they have different structural formulae / different structures [1] (ii) CH3-CH2-CH=CH-CH3 / any other correct isomer [1] (b) (i) CH2-(Br)-CH2Br [1] NOT: C2H4Br2 dibromoethane [1] NOTE: numbers not required but if given must be 1, 2 (ii) CH3-CH2-CH3 [1] NOT: C3H8

propane [1]

(iii) CH3-CH2-CH2-CH2-OH / CH3-CH2-CH(OH)-CH3 [1] butanol [1] numbers not required but if given must be correct and match formula (c) (i) CH3-CH=CH-CH2-CH3 [1] CH3-CH=CH-CH3 [1] (ii) pink / purple [1] colourless [1] NOT: clear (d) -CH2-CH(CN)-CH2-CH(CN)- correct repeat unit CH2-CH(CN) [1] COND: at least 2 units in diagram [1] continuation [1] [Total:16]




6 (a) (i) (attractive force between) positive ions [1] and (negative) electrons [1] opposite charges attract ONLY [1] electrostatic attraction ONLY [1] (ii) lattice / rows / layers of lead ions / cations / positive ions [1] NOT: atoms / protons / nuclei can slide past each other / the bonds are non-directional [1] (b) (i) anhydrous cobalt chloride becomes hydrated [1] ACCEPT: hydrous (ii) carbon dioxide is acidic [1] sodium hydroxide and calcium oxide are bases / alkalis [1] (iii) Any two of: water, calcium carbonate and sodium carbonate [2] ACCEPT: sodium bicarbonate (c) number of moles of CO2 formed = 2.112 / 44 = 0.048 [1] number of moles of H2O formed = 0.432 / 18 = 0.024 [1] x = 2 and y = 1 NOT: ecf from this line formula is 2PbCO3.Pb(OH)2 / Pb(OH)2. 2PbCO3 [1] [Total:12] 7 (a) (i) hydrogen (atoms) replaced by (atoms) of a different element e.g. chlorine [1] NOT: substitute (ii) light required [1] (b) exothermic reaction gives out energy [1] endothermic reaction absorbs takes in energy [1] (c) bonds broken energy C-H +412 Cl-Cl +242 total energy +654 [1] bonds formed energy C-Cl –338 H-Cl –431 total energy –769 [1] energy change –115 [1] negative sign indicates exothermic [1] [Total: 8]




0620 CHEMISTRY


This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October / November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.





1 (a) C and F [1] (b) A [1] (c) B [1] (d) D [1] (e) E [1] (f) A and D [1] [Total: 6] 2 (a) (i) two atoms per molecule [1] (ii) 7e in outer shell or level / same number of outer electrons / need to gain one electron [1] (iii) different number of energy levels / different number of electrons [1] (iv)

halogen solid, liquid or gas at room temperature

colour

chlorine

gas yellow / yellow green / green

bromine liquid brown / red-brown / orange-brown

not: red / orange

iodine solid black / grey / silver-grey / purple / violet

NOT: blue-black

NOTE: one mark for each vertical column [2] (b) correct formula, AsF3 [1] 3nbps and 1bp around all 3 fluorine atoms [1] 3bps and 1nbp around arsenic atom [1] (c) (increased) light increases / causes forward reaction / light causes AgCl reacts with CuCl [1] (increased) light increases the amount of silver (and so darkens glass) [1] decrease in light reverses reaction / uses up silver / silver reacts (and so reduces darkness)[1] [Total: 11]




3 (a) (i) the (forward) reaction is endothermic [1] (ii) none [1] volume of reactants and products the same [1] ACCEPT: number of moles or molecules (iii) the reaction (between oxygen and nitric oxide) is exothermic [1] high temperatures push equilibrium to left / high temperatures decrease yield of products

/ low temperatures favour forward reaction [1] (iv) 4NO2 + O2 + 2H2O � 4HNO3 [2] not balanced = (1) only (v) (cost of) high amount of electricity / energy [1] (b) (i) contains more nitrogen [1] (ii) photosynthesis [1] chlorophyll is catalyst / chlorophyll absorbs light [1] carbon dioxide and water react [1] to make glucose / carbohydrates / starch / sugar / named sugar [1] [Total: 13] 4 (a) Any one of: Fe2O3 + 3C � 2Fe + 3CO 2Fe2O3 + 3C � 4Fe + 3CO2 Fe2O3 + 3CO � 2Fe + 3CO2

for correct equation (2) not balanced = (1) only any four of: coke burns to form carbon dioxide / C + O2 � CO2 this reacts with more carbon to form carbon monoxide / C + CO2 � 2CO calcium carbonate decomposes to form calcium oxide and carbon dioxide / CaCO3 � CaO +

CO2 calcium oxide / calcium carbonate reacts with silica / silicon oxide / silicon(IV) oxide (in ore)

to form calcium silicate / slag / CaO + SiO2 � CaSiO3 or CaCO3 + SiO2 � CaSiO3 + CO2 the reaction between carbon and oxygen is exothermic / produces heat / coke is used as a

fuel / the slag floats on the (molten) iron / the slag and molten iron can be run off separately [6]




(b) (i) greenhouse effect / CO2 is a greenhouse gas [1] global warming / ice caps melting / suitable example [1] (ii) burning or combustion of charcoal produces carbon dioxide [1] trees use carbon dioxide (in photosynthesis) [1] (iii) cathode reaction Fe3+ + 3e � Fe [1] anode reaction 2O2- � O2 + 4e [2] not balanced = (1) only [Total: 13] 5 (a) because they have more than one oxidation state or valency / form ions with different

charges [1] there are two iron oxides (iron(III) oxide and iron(II) oxide) / iron forms Fe2+ and Fe3+

compounds / iron forms iron(II) and iron(III) compounds [1] (b) (i) to remove the precipitate / remove the silver(I) chromate(VI) / remove the residue [1] (ii) to remove soluble impurities / remove named soluble salt e.g. potassium nitrate / remove

reactants [1] (iii) to dry solid / to remove water [1] (c) (i) need one mole of potassium chromate(VI) for two moles of silver(I) nitrate / correct

references to mole ratio [1] (ii) mass of AgNO3 needed is 170 × 0.2 × 0.1 = 3.4g [2] NOTE: if answer given is 34 they have omitted 0.1 ALLOW: (1) ecf (iii) number of moles of AgNO3 used = 0.02 × 0.2 = 0.004 [1] number of moles of Ag2CrO4 formed = 0.002 [1] mass of one mole of Ag2CrO4 = 332g mass of Ag2CrO4 formed = 0.664g [1] NOTE: use ecf when appropriate [Total: 11]




6 (a) (i) Cu(OH)2 � CuO + H2O [1] (ii) Rb [1] (b) (i) electron loss [1] (ii) because they can accept electrons [1] (c) (i) copper and mercury [1] (ii) add copper / mercury / metal to (named) acid and no reaction / no bubbles / no

hydrogen [1] (d) (i) Mn [1] (ii) (solution) becomes colourless / decolourises NOT: clear [1] [Total: 8] 7 (a) (i) contains only carbon, hydrogen and oxygen [1] hydrogen (atom) to oxygen (atom) ratio is 2:1 [1] ALLOW: C:H:O as 1:2:1 or Cn(H2O)n (ii) condensation [1] polymerisation [1] (b) (i) cells / micro-organisms / plants / animals / metabolic reactions [1] obtaining energy from food / glucose / nutrients [1] (ii) 2C2H5OH + 2CO2 [2] allow: C2H6O for C2H5OH not balanced = (1) only (iii) to prevent aerobic respiration / to get anaerobic respiration / to prevent ethanoic acid /

lactic acid / carboxylic acids being formed / to prevent oxidation of ethanol [1] (c) displayed formula of methyl butanoate [2] NOTE: all bonds must be shown NOTE: award (1) if error in alkyl groups but correct displayed structure of –COO– (d) (i) alcohol, e.g. glycerol, circled [1] ALLOW: if only part of glycerol molecule is circled as long as it involves an OH group (ii) saturated correct reason based on group C17H35 / all C–C bonds / no C = C bonds [1]




(iii) salt / carboxylate / alkanoate [1] (making) soap [1] ACCEPT: detergent / washing (e) at least one correct amide linkage –CONH– [1] continuation shown at both ends of chain [1] diagram showing three (different) amino acid residues [1] [Total: 18]




0620 CHEMISTRY


This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.





1 (a) same number of protons [1] same number of electrons [1] different number of neutrons [1] (b) (i) 235U / 239Pu [1] NOTE: need symbol or name and nucleon number (ii) treating cancer / chemotherapy / radiographs / tracer studies / x–ray (scans) /

sterilise surgical instruments / diagnose or treat thyroid disorders / radiotherapy [1]

paper thickness / steel thickness / radiographs / welds / tracing / fill levels in packages / food irradiation / smoke detectors [1] ACCEPT: any other uses

(iii) Zr + 2H2O � ZrO2 + 2H2 [2] not balanced = (1) only (iv) hydrogen explodes / fire (risk) [1] (c)

if the oxide is predicted result with hydrochloric acid

predicted result with aqueous aqueous sodium hydroxide

acidic NR R

neutral NR NR

basic R NR

amphoteric R R

(1) per line [4]

[Total: 13]




2 (a) (i) positive and negative ions [1] regular pattern / opposite charges closer than the same charge [1] (ii) so that charges cancel / ions may not have the same charge [1] (iii) Any three of:

high melting point or boiling point hard brittle soluble in water / insoluble in organic solvents conduct (electricity) in liquid state or in aqueous solution / non-conductors or poor conductor (when solid) [3]

(b) correct formula [1]

correct charges [1] 6x and 2o around oxygen [1]

[Total: 9] 3 (a) (i) roast or heat or burn in air / roast or heat or burn in oxygen [1] need both of the above (ii) ZnO + C � Zn + CO / 2ZnO + C � 2Zn + CO2 / ZnO + CO � Zn + CO2 [1] (b) (i) ZnO + H2SO4 �ZnSO4 + H2O [1] (ii) zinc reduces / gives electrons / displaces (copper / cobalt / nickel ions) [1] forming copper / cobalt / nickel (metal which is precipitated) [1] (c) (i) Zn2+ + 2e � Zn [1] (ii) OH– � 2H2O + O2 + …..e (1) only 4OH– �2H2O + O2 + 4e [2] (iii) sulfuric acid / hydrogen sulfate [1] ACCEPT: sulfuric acid




(d) (i) Any two of: appearance more resistant to corrosion harder (accept stronger) easier to cast [2] (ii) zinc more reactive (than iron or steel) [1] zinc loses electrons [1] electrons move (from zinc) to iron [1]

zinc reacts (with air and water) / zinc corrodes / is oxidised / forms positive ions / anodic or iron and steel don’t react (with air and water) / not oxidised / do not form ions / do not lose electrons [1]

[Total: 15] 4 (a) (i) S + O2 � SO2

or sulfur burnt / roasted / heated in air to form sulfur dioxide [1]

2SO2 + O2 2SO3 [2] unbalanced = (1) only (catalyst) vanadium(V) oxide / vanadium pentoxide [1] (temperature) 440 to 460

oC [1] (dissolve) sulfur trioxide in sulfuric acid (to form oleum) [1] ignore comments about pressure (ii) add oleum to water [1] (b) Ba(C6H13SO3)2 / (C6H13SO3)2Ba [1] (c) (i) � magnesium hexanesulfonate + hydrogen [1] (ii) � calcium hexanesulfonate + water [1] (iii) 2C6H13SO3H + Na2CO3 � 2C6H13SO3Na + CO2 + H2O C6H13SO3Na = (1) [1] remaining species correct and equation balanced = (1) [1]




(d) (i) measure pH / add universal indicator [1] both acids have a low value / pH 0–2 / same colour / red [1] or measure rate with named reactive metal, Mg, Zn (1) both fast reactions (1) or measure rate using piece of insoluble carbonate, CaCO3 (1) both fast reactions (1) NOTE: must be insoluble for first mark or measure electrical conductivity (1) both good conductors (1) (ii) to have same concentration of H+ / one acid is H2SO4, the other is C6H13SO3H / sulfuric

acid is dibasic, hexanesulfonic is monobasic [1] (iii) a strong acid is completely ionised, [1] a weak acid is partially ionised [1] [Total: 17] 5 (a) protective / layer and of oxide [1] (b) correct repeat unit [1] continuation shown [1] (c) (i) catalyst [1] biological / protein [1] (ii) hydrochloric acid / any strong acid / any strong alkali [1] (iii) amino acids [1] (iv) chromatography [1] (v) nylon / kevlar [1] (d) (i) non-biodegradable [1] (ii) CH2=CH(C6H5) [1] [Total: 11]




6 (a) (i) CH3–CH2–CH2–OH [1] NOT: C3H8O between 2030 and 2050 [1] (ii) C5H11OH + 7½ O2 � 5CO2 + 6H2O [1] (b) any three from: same general formula same functional group same chemical properties same methods of preparation accept consecutive members differ by CH2 [3] (c) (i) same molecular formula [1] different structures / different structural formulae [1] (ii) CH3–CH2–CH(OH)–CH3 / (CH3)3C–OH [1] (d) (i) number of moles of glucose = 72/180 = 0.4 [1] maximum number of moles ethanol = 0.8 [1] maximum mass of ethanol, Mr = 46 g, 0.8 × 46 = 36.8 g [1] or 180 (g) produces 2 × 46 = 92 (g) (1) (72 (g) produces) 72/180 × 92 (1) = 36.8 (g) (1) (ii) crack (petroleum or alkane) [1] react with water / hydrate (ethene to make ethanol) [1] conditions for cracking

(temperature) 450to 800

oC / (catalyst) zeolites / aluminosilicates / silica / aluminium oxide / alumina / china / broken pot / chromium oxide

or conditions for hydration (temperature) 300

oC / (pressure) 60 atmospheres / (catalyst) phosphoric acid [1] [Total: 15]




0620 CHEMISTRY






1 (a) A, D, E (1) same number of protons and electrons / electrically neutral (1) [2] (b) C (1) more electrons than protons / 36e– and 34p+

/ it has gained electrons (1) [2] (c) B, F (1) [1] (d) they have same number of protons (1) different number of neutrons / neutron number (1) [2] [Total: 7] 2 (a) (i) filtration (1) chlorination (1) [2] (ii) Any two from: [2]

• manufacture of ethanol

• used in the manufacture of sulfuric acid or in the Contact process

• manufacture of hydrogen or ammonia or for the Haber process (iii) Any two from: [2]

• cooking

• washing or laundry

• drinking

• toilets

• watering plants

• (domestic) heating (b) boiling or turning to steam (1) then condensing / condensation (1) [2] [Total: 7] 3 (a) (i) (particles) spread to fill total available volume / move from high concentration

to low concentration / moves down a concentration gradient (1) [1] (ii) mass or Mr (1) [1] (b) (i) helium atoms / molecules are lighter than molecules in air or N2 and O2

or helium is less dense than air or N2 and O2. or helium diffuses (through the porous barrier) faster than air or N2 and O2. (1) [1]




(ii) faster rate of diffusion / molecules move faster (at high temperatures). (1) [1] (c) (i) CH4 + 2O2 → CO2 + 2H2O (1) [1] (ii) would get a mixture of helium and carbon dioxide or would get a mixture of gases or waste of methane / natural gas / fossil fuel (1) [1] (iii) fractional distillation (1) [1] [Total: 7] 4 (a) (i)

Group number

I II III IV V VI VII

symbol Na Mg Al Si P S Cl

number of valency electrons

1 2 3 4 5 6 7

valency 1 2 3 4 3 2 1

(1) for each line [2] (ii) number of valency electrons = the group number (1) [1] (iii) for Na to Al

the valency is the same as the number of valency (outer) electrons (1) (because) this is the number of electrons lost (for full energy level) (1) for P to Cl

the valency is 8 – [number of valency (outer) electrons] or valency + valency electrons = 8 (1) (because) this is number of electrons needed (or to be gained) (for full energy level) (1)

(b) (i) Assume change is from L to R unless clearly stated:

basic to amphoteric to acidic (2) [2] (ii) ionic (metal) chlorides on the left (1)

covalent (non-metal) chlorides on the right (1) [2] [Total: 11]




5 (a) M1: (zinc sulfide) heated / roasted / burnt in air (1) M2: zinc oxide formed (1) M3: zinc oxide reduced (1) M4: (by adding) coke or carbon (1) M5: Balanced equation (any one of) (1) [5] 2ZnS + 3O2 → 2ZnO + 2SO2

2ZnO + C → 2Zn + CO2

ZnO + C → Zn + CO

ZnO + CO → Zn + CO2

(b) Any two from: [2]

• (making) brass or alloys (1)

• galvanising (1)

• sacrificial protection (1)

• batteries (1)

[Total: 7]

6 (a) (i) rate at t2 less than at t1 or the rate decreases (1)

rate at t3 zero / reaction stopped (1) [2] (ii) rate at t2 less than at t1 because concentration of hydrogen peroxide is less

at t2 or concentration of hydrogen peroxide is decreasing. (1) (rate at t3 zero / reaction stopped because) hydrogen peroxide is used up (1) [2]

(b) (i) steeper and must come from the origin (1)

final volumes the same (1) [2]

(ii) Any two from: [2] steeper curve because of a faster rate faster rate because of increased surface area same amount / volume / mass / no of mol of hydrogen peroxide ecf for M1 for a shallower curve because of slower rate.




(c) filter (and rinse / wash) (1) dry manganese (IV) oxide (1) weigh / measure mass manganese(IV) oxide after reaction (1) the mass should be 0.1 g or unchanged. (1) [4]

(d) number of moles of O2 formed = 0.096 / 24 = 0.004 (1)

number of moles of H2O2 in 40 cm3 of solution = 0.004 × 2 = 0.008 (1) concentration of the hydrogen peroxide in mol / dm3 = 0.008 / 0.04 = 0.2 (1) [3]

[Total:15] 7 (a) (i)

aqueous solution

lead Pb

magnesium Mg

zinc Zn

silver Ag

lead (II) nitrate

� � �

magnesium nitrate

X� � �

zinc nitrate

� � �

silver(I) nitrate

� � �

each horizontal line correct (1) [3] (ii) Zn (1)

An arrow from Zn to Zn2+ (1) [2]

(iii) Zn + 2Ag+ → Zn2+ + 2Ag (1) [1] (b) (i) correct direction from zinc to lead (1) [1] (ii) metals react by losing electrons (1)

the more reactive metal / zinc will lose electrons more readily (making the electrode negatively charged). (1) [2]




(iii) manganese and zinc are more reactive than lead (and / or copper) (1) lead is more reactive than copper (1) [2] (iv) the polarity of a Mn / Zn (cell) or the voltages of Zn / Pb and Mn / Pb (cells) (1) [1] [Total: 12] 8 (a) (i) CH3–CH=CH–CH3 (1) [1] (ii) one correct amide linkage between two rectangles (1)

correct sequencing of a second amide link and monomers (1) two correct amide links and rest of structure correct (including additional monomers if seen) and correct continuation bonds (1) [3]

(iii) protein or polypeptide or named protein (1) [1] (iv) addition: only the polymer or one product is formed (1)

condensation: the polymer and a small molecule / water / HCl is formed (1) [2]

(b) (i) does not break down or rot or decompose (1) by microbes or fungi or bacteria or by living organisms (1) [2] (ii) Any three from: [3] visual pollution (1)

(shortage of) landfill sites (1) danger to wildlife / animals (including at sea) (1) toxic gases when burnt or greenhouse gases produced when burned (1)

(c) Any two from: [2]

resistant to corrosion / unreactive to water / more durable (1) lighter / less dense (1) easier to manufacture / can be moulded (1) good insulator / keeps the water cold (1)

[Total: 14]




0620 CHEMISTRY






1 (a) A and E need both (1) [1] (b) D (1) [1] (c) C (1) [1] (d) B (1) [1] (e) F (1) [1] (f) E (1) [1] (g) C (1) [1] [Total: 7] 2 (a) (i) substance / material / compound / element / mixture (burnt) to produce / release

energy or heat (1) [1] (ii) Any two from:

coal coke peat petroleum / crude oil refinery gas / LPG gasoline / petrol naptha kerosene / paraffin diesel (oil) / gas oil fuel oil propane butane [2]

(iii) wood / charcoal / animal dung / biomass / Uranium / U / plutonium / Pu (1) [1]




(b) (i) any two from: water / steam / water vapour / H2O (1) carbon dioxide / CO2 (1) carbon monoxide / CO (1) [2]

(ii) any two from:

limited or finite resource / non-renewable / will run out / depleted (1) greenhouse effect / gas(es) / climate change / (cause) global warming (1) acid rain (1) production of poisonous / toxic gases (1) [2]

[Total: 8] 3 (a) (i) pressure 150–300 atmospheres / atm (1)

temperature accept in range 370 to 470 °C (1) iron (catalyst) (1)

balanced equation N2 + 3H2 � 2NH3 (1)

equilibrium / reversible (1) [5]

(ii) potassium / K (1)

phosphorus / P (1) [2]

(b) (i) burn fossil fuels / burn fuels containing sulfur / burn compounds containing

sulfur / burn ores containing sulfur / roast metal sulfides / burn metal sulfides (1)

sulfur dioxide / SO2 (formed) (1)

(form) sulfuric / H2SO4 / sulfurous acid / H2SO3 (1) OR nitrogen and oxygen (in air) react at high temperatures / in jet engines / car engines / lightning. (1) (form) oxides of nitrogen (1) (form) nitric acid / HNO3 / nitrous acid / HNO2 (1) [3]




(ii) any two from: calcium oxide / lime / quicklime / CaO (1) calcium hydroxide / Ca(OH)2 / lime / slaked lime / limewater (1) calcium carbonate / CaCO3

/ limestone / chalk / marble (1) [2] guidance: ‘lime’ can only be credited once.

[Total: 12] 4 (a) (i) butanoic / butyric acid (1) CH3CH2CH2COOH / C2H5CH2COOH (1) [2] (ii) any three from: (same) general formula (1) (consecutive members) differ by CH2 (1) same functional group (1) common methods of preparation (1)

physical properties vary in predictable manner / show trends / gradually change or example of a physical property variation i.e. melting point / boiling point / volatility (1) [3]

(b) (i) displayed formula of propan-1-ol, all bonds shown separately (1) [1] (ii) acidified (1) potassium manganate(VII) / potassium permanganate / KMnO4 or potassium

dichromate(VI) / K2Cr2O7 / potassium dichromate (1) [2] (c) (i) zinc + propanoic acid → zinc propanoate (+ hydrogen) (1) [1] (ii) calcium oxide + propanoic acid → calcium propanoate + water (1) [1] (iii) LiOH + CH3CH2 COOH → CH3CH2COOLi + H2O (1) [1] (d) (i) concentration (of acid in C) is less / halved or concentration of A is more /

doubled. (1) less collisions or more collisions in A (than in C) (1) [2] (ii) (higher temperature in B particles / molecules / atoms) move faster / have

more energy / more have Ea or (particles / molecules / atoms) in A move slower / have less energy / less have Ea (1)

more collisions or less collisions in A (than in B) (1) [2]




(iii) It (D) has strong (acid) and A has weak acid / (D) stronger / (D) ionises more / (D) dissociates more or A is weaker / A ionises less / A dissociates less (1)

It (D) has higher concentration of hydrogen ions or A has a lower

concentration of hydrogen ions (1) more collisions (in D) or fewer collisions in A (1) [3] [Total: 18] 5 (a) (i) incomplete combustion or limited oxygen / less oxygen / not enough oxygen

(1) [1] (ii) any two from: (forward) reaction is endothermic (1) high temperature increases yield / favours forward reaction / shifts equilibrium

to right (1) faster reaction (rate) (1) [2] (iii) any two from: high pressure reduces yield or favours LHS (1) because LHS has smaller volume or number of moles / number of molecules

(of gas) ORA (1) (high pressure plant is) expensive / dangerous / explosion / leaks [2] 5 (b) hydrogen and chlorine / H2 and Cl2 (1) sodium hydroxide / NaOH / Na+OH– (1) 2H+ + 2e → H2 / 2H+ → H2 – 2e (1) 2Cl

– → Cl2 + 2e / 2Cl – – 2e → Cl2 (1)

Hydrogen / H2

/ H / H+ at cathode and chlorine / chloride / Cl2

/ Cl / Cl – at anode (1) [5]

5 (c) each chlorine 1 bond pair and 3 non-bond pair (1) oxygen atom 2 non-bond pairs and 2 bond pairs as double bond (1) carbon atom 4 bond pairs including 2 bond pairs as double bond (1) [3] [Total: 13]




6 (a) any three from: (it would have) more than one or variable valency / oxidation state / oxidation

number (1) (metal / element / titanium / it has a) high density (1) coloured compounds / ions / solutions (1) form complex (ions) (1) (element/compound act as) catalyst (1) [3] (b) ScF3 (1) correct charges on both ions (1) 8 electrons around (each) fluoride (1) [3] (c) name or formula of strong acid and alkali (1) reacts with or neutralises both acid and base or alkali (then amphoteric) (1) it dissolves / soluble in both(acid and alkali) or form solutions in both (1) [3] [Total: 9] 7 (a) repeat without indicator / repeat using same volumes of acid and alkali or use

carbon / charcoal to remove indicator (1) evaporate / heat / warm / boil / leave in sun (1) until most of the water has gone / some water is left / saturation (point) /

crystallisation point (1) leave / allow to cool / allow to crystallise (1) filter (off crystals) / wash(with distilled water) / dry crystals with filter paper / dry

crystals in warm place / oven / windowsill (1) [5] (b) 0.062 (1) 0.031 (1) 3.97 g (1) 55.4% (1) [4]




(c) (i) (to prove) all water driven off or evaporated or boiled / no water remains / to make salt anhydrous (1)

(ii) m1– m2 = mass of water (1)

(calculate) moles of water AND moles of hydrated or anhydrous salt (1) 1:1 ratio / should be equal (1) [3]




0620 CHEMISTRY






1 (a) carbon dioxide (1) [1] (b) propene (1) [1] (c) krypton (1) [1] (d) nitrogen (1) [1] (e) fluorine (1) [1] (f) sulfur dioxide (1) [1] (g) hydrogen (1) [1]

[Total: 7]

2 (a) any three from: particles have more energy (1) move faster (1) collide more frequently (1) more particles have energy greater than Ea [3] guidance: more colliding molecules have enough energy to react is worth (2) (b) particles move in all directions / randomly in both liquids and gases (1) no bonds / very weak forces between particles in gases (1) molecules can move apart / separate (to fill entire volume) (1) OR bonds / forces / IMF between particles in liquids (1) molecules cannot move apart / separate (so fixed volume in liquids) (1) [3] [Total: 6] 3 (a) (i) enzymes (1) [1] (ii) reduces growth of microbes / rate of reproduction of microbes is lower /

microbes are dormant (1) fewer (enzymes) to decay food (1) OR enzymes less efficient at lower temperatures (1) slower reaction rate (1) [2] (b) correct linkage (1) rest of molecule correct and continuation shown (1) (other product is) water (1) [3]




(c) any three from: photosynthesis (1) light / photochemical (1) chlorophyll / chloroplasts (1) carbon dioxide and water needed (1) (glucose and) oxygen (1) [3] [Total: 9]

4 (a) (i) heat limestone / calcium carbonate (1) fractional distillation (1) liquid air (1) [3] (ii) any two of the oxides, C, S, P and Si, mentioned (1) carbon dioxide and sulfur dioxide escape / are gases (1) phosphorus oxide or silicon(IV) oxide react with calcium oxide / phosphorus oxide or silicon(IV) oxide are acidic and calcium oxide is basic (1) to form a slag or calcium silicate or calcium phosphate (1) must have correct equation for one of the above reactions (1) [5] (b) (i) lattice / rows / regular arrangement of cations / positive ions / Fe2+ (1) mobile / free / delocalised / sea of electrons (1) [2] (ii) the rows of ions / ions can move past each other (1) without the metal breaking / bonds are not directional / not rigid (1) [2] (iii) carbon particles / atoms different size (1) prevents movement of rows, etc. (1) [2] [Total: 14] 5 (a) faster reaction rate (1) higher collision rate (1) greater yield or favour RHS (1) pressure favours products because it has lower volume / fewer product molecules (1) [4] (b) higher temperature favour endothermic reaction (1) this is the back reaction / left hand side / reactants (1) reduce yield (1) [3] (c) (i) greater surface area (1) [1] (ii) increase reaction rate (1) can use a lower temperature to have an economic rate (1) and not decrease yield (by increasing temperature). [2]




(d) lower the temperature (1) only ammonia will liquefy (1) OR add water (1) only ammonia will dissolve (1) OR increase pressure (1) only ammonia will liquefy (1) [2]

(e) second line +3 × 155 = + 465

third line –3 × 280 = (–)840

fourth line –3 × 565 = (–)1695 all three correct (2) two correct (1) 1170 + 465 = 1635 840 + 1695 = 2535 both numerically correct (1) exothermic reaction with some reasoning (1) [4]

[Total: 16]

6 (a) (i) C and H only (1) [1] (ii) only single bonds (1) [1] (b) (i) CnH 2n+2 (1) [1] (ii) C14H30 (1)

(14 × 12) + 30 = 198 (g) (1) [2] (c) (i) C9H20 + 14 O2 → 9CO2 + 10H2O (2) [2] (ii) Volume ratio CxHy(g) + O2(g) → CO2(g) + H2O(l) 20 160 100 all in cm3

1 8 5 mole ratio C5H12 + 8O2 → 5CO2 + 6H2O For evidence of method (1) for equation as above (2) [3] (d) (i) alkanes in petrol / fuel / solvent (1) alkenes to make alcohols / plastics / polymers / solvents (1) hydrogen to make ammonia / fuel / fuel cells, etc. (1) [3] (ii) a correct equation for example: C10H22 → C8H16 + C2H4 + H2 (1) [1]




(e) (i) light or lead tetraethyl / catalyst / high temperature (1) [1] (ii) CH3–CHCl–CH3 (1) [1] [Total: 16] 7 (a) bauxite (1) [1] (b) electrolyte alumina / aluminium oxide dissolved in molten cryolite (1) use cryolite to reduce mp / comparable idea / temperature of electrolyte 900 to

1000

°C (1) electrodes carbon (1) aluminium formed at cathode / Al 3+ + 3e → Al (1) oxygen formed at anode / 2O2– → O2 + 4e (1) anode burns / reacts to carbon dioxide / C + O2 → CO2 (1) [6] (c) (i) food containers / window frames / cooking foil / cars / bikes / drink cans (1) [1] (ii) 4OH– → O2 + 2H2O + 4e (2) [2] 4Al + 3O2 → 2Al2O3 (2) [2] [Total: 12]

Chemistery P3 Merged

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