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© Edexcel Limited 2007Extension Units Science Teacher’s Guide96

Answers ➞ continuedC3.3

C3.3 1 Water, water everywhere

Students’ Book pages

1 Because it can contain dissolved substances hazardous to health and/or it can contain harmful bacteria.

2 Drinking, cooking and cleaning.

3 Check what chemicals/additives are present and measure the amount.

4 Qualitative and quantitative.

5 To set limits for chemical content so water is safe to drink.

6 a Fertilisers and pesticides; b detergents, bleaches and drain cleaners.

7 Analytical chemists check the purity of the water, analysing what substances are present and how much of each. This is important as the results of the analysis are checked against government standards for healthy and safe drinking water.

Summary exercise

cleaning, drinking, 70% survive, analytical, farms, qualitative, quantitative

Higher questions

1 Dehydration and water-born diseases.

2 Carbonates from rocks and other soluble minerals.

3 a Qualitative; b quantitative; c quantitative.

Extension questions

1 a 3.5 g; b 3.5%; c 0.10675 g;d any two from: sodium chloride Na+Cl– ;

magnesium �g2+SO 2– 4 ; sodium (Na+)

2SO 2– 4 ;

magnesium chloride(�g+Cl–)2.

Worksheet C3.3 1a

1 2 litres (dm3).

2 Lose more through sweating.

3 Washing, cooking, cleaning and in factories.

4 Convenient and good for health.

5 As water runs through rocks that contain soluble minerals.

6 It gives information on what ions are present, and how much of each ion is present.

7 Cations are positive; anions are negative.

8 Any two from: calcium chloride, magnesium chloride, sodium chloride, potassium chloride, etc. (Same metals with nitrate, sulphate and bromide.)

9 To make sure it is safe to drink.

10 Disagree: all water contains ions, in most case the concentrations are too low to have any effect.

Worksheet C3.3 1b

1 Tea.

2 To remove particles of matter.

3 Aluminium sulphate, Al2(SO4)3

4 No: our water runs through rocks that contain soluble minerals.

5 20 tons of aluminium sulphate were poured into the wrong tank.

6 a Qualitative; b quantitative.

7 It caused damage to the digestive system and brain damage to some people.

8 a Double-checks when delivering chemicals;b analyse the water supply more often.

9 Considerable brain damage greatly affects both the victim and their family, changing their lives for ever. This would require substantial compensation for years of suffering and work lost.

10 It was a long time after the accident.

C3.3 2 Testing for ions


1 �etals and non-metals.

2 a Positive ions; b negative ions.

3 To have no doubt about the results of the test.

4 Different ionic compounds can have the same colour/appearance.

5 Copper.

6 a Test what ion is present, not how much;b because lithium and strontium produce the same

colour of flame.

7 Because there are two ions in each ionic compound.

Summary exercise

ions, cation, anion, ionic, two, unique, flame, yellow, green

AnswersC3.3

© Edexcel Limited 2007 Extension Units Science Teacher’s Guide 97

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Higher questions

1 a Cu Cu2++2e–

b O2+4e– 2O2–

c Al Al3++3e–

d Br2+2e– 2 Br–

2 Different electron arrangements (shells).

Extension questions

1 a Identifying an unknown powder found at the crime scene and on a suspect.

b Testing products from factories and comparing them with pollutants in water.

c Yellow flame shows sodium present (salt is sodium chloride).

Worksheet C3.3 2b

1 2.

2 Cations, by losing electrons and anions by gaining electrons.

3 �etals have one, two or three electrons in their outer shell, and it is easier to lose electrons to get a full outer shell. Non-metals have five, six or seven electrons in their outer shell, and it is easier to gain electrons to get a full outer shell.

4 a Ca Ca2++2e–

(2,8,8,2) (2,8,8)b O+2e– O2–

(2,6) (2,8)c Al Al3++3e–

(2,8,3) (2,8)

5 a

K CI K+ CI–

+ –

b

�g O �g2+ 02–

2+ 2–

6 The rocks and minerals through which the water runs.

C3.3 3 Looking for cations


1 They don’t all produce unique colours.

2 Hydrochloric acid or nitric acid.

3 a Aluminium hydroxide; b calcium hydroxide.

4 a Iron(III); b calcium or aluminium.

5 a CaCl2(aq)+2NaOH(aq) Ca(OH)2(s) +2NaCl(aq) (white)

b Fe(NO3)3(aq)+3NaOH(aq) Fe(OH)3(s) +3Na NO3(aq) (brown)

6 a Blue precipitate; b green precipitate.

7 a Add sodium hydroxide solution and white precipitate forms, which can redissolve if excess sodium hydroxide is added.

b Add sodium hydroxide solution, no precipitate, heat and alkaline gas given off, test with moist universal indicator paper.

Summary exercise

hydroxide, cations, ammonium, no, alkaline, aluminium, dissolves, calcium, blue, iron(II), brown

Higher questions

1 ammonium chloride+sodium hydroxide sodium chloride+water+ammonia

NH4+Cl–(aq)+NaOH(aq) NaCl(aq)+H2O+NH3

2 a Al(OH)3+3NaBr; white precipitateb Cu(OH)2+2NaCl; blue precipitatec Ca(OH)2+2NaI; white precipitate

Extension questions

1 a Zn(NO3)2(aq)+2NaOH(aq) Zn(OH)2+2Na(NO3)b Calcium ions also produce white precipitate with

sodium hydroxide.

Worksheet C3.3 3b

Part A

1

Cation Symbol Effect of adding sodium hydroxide solution

a aluminium Al3+(aq) white precipitate

b iron(II) Fe2+(aq) green precipitate

c copper(II) Cu2+(aq) blue precipitate

d calcium Ca2+(aq) white precipitate

e iron(III) Fe3+(aq) brown (rust) precipitate

f ammonium NH4+(aq) no precipitate


Answers ➞ continuedC3.3 Answers ➞ continuedC3.3

2 a 3NaNO3(aq); sodium hydroxideb FeSO4(aq); Fe(OH)2(s)

sodium hydroxide; sodium sulphatec 2NaOH(aq); +(Na)2SO4(aq) copper(II) sulphate; copper(II) hydroxided Ca(NO3)2(aq); Ca(OH)2(s) sodium hydroxide; sodium nitratee 3NaOH(aq); 3NaNO3 iron(III) nitrate; iron(III) hydroxide

3 Add excess sodium hydroxide and heat, the aluminium precipitate will re-dissolve.

4 Precipitations.

Part B

1 a Blue; b none; c pink; d none; e yellow/orange.

2 Iron(II) ions are green.

3 Lithium, sodium, magnesium, chloride, sulphate and nitrate.

4 Dichromate is a negative ion.

5 a Yellow/orange; b pink.

6 �ore than one ion can produce the same colour.

C3.3 4 Detecting acids


1 a Substances that change colour in acid solutions;b litmus and universal indicator.

2 Sulphur dioxide from burning fossil fuels.

3 H+ ions.

4 a Effervescence.b Hydrogen gas produced in image B and carbon

dioxide gas produced in image C.

5 sulphuric acid+magnesium magnesium sulphate+hydrogen H2SO4+�g �gSO4+H2

6 sulphuric acid+copper(II) carbonate copper(II) sulphate+water+carbon dioxide H2SO4+CuCO3 CuSO4+H2O+CO2

7 a salt+hydrogenb salt+water+carbon dioxide

8 Universal indicator turns red/orange, adding magnesium produces hydrogen gas and adding sodium carbonate produces carbon dioxide gas.

Summary exercise

H+, indicators, acid, litmus, universal, red, metals, carbonates, �g, hydrogen, CuCO3, carbon dioxide

Higher questions

1 Damages life in lakes and rivers, damages trees and buildings.

2 b sodium chloride+water+carbon dioxide NaCl+H2O+CO2 2HCl+Na2CO3 2NaCl+H2O+CO2c iron(II)+water+carbon dioxide FeSO4+H2O+CO2 H2SO4+FeCO3 FeSO4+H2O+CO2d magnesium nitrate+hydrogen �g(NO3)2+H2 2HNO3+�g �g(NO3)2+H2e zinc(II) chloride+water+carbon dioxide ZnCl2+H2O+CO2 2HCl+ZnCO3 ZnCl2+H2O+CO2

Extension questions

1 a 2H3PO4(aq)+3CuCO3(s) Cu3(PO4)2(s)+3H2O(aq)+3CO2(g)

b 2H3PO4(aq)+3�g(s) �g3(PO4)2(s)+3H2(g)

Worksheet C3.3 4b

1 Hydrogen (H+) ion.

2 a Litmus – red; universal indicator – red, orange and yellow.

b Universal indicator as it gives different colours with different pH numbers.

3 a nitric acid+magnesium magnesium nitrate +hydrogen

2HNO3+�g �g(NO3)2+H2b nitric acid+magnesium carbonate

magnesium nitrate+water+carbon dioxide 2HCl+�gCO3 �g(NO3)2+H2O+CO2c i hydrogen ii salt; carbon dioxide

4 Limewater turns milky.

5 Burns with a pop.

6 a hydrochloric acid+copper(II) oxide copper(II) chloride+water

2HCl+CuO CuCl2+H2Ob i Best, copper(II) carbonate; ii worst, copper.

C3.3 5 Looking for anions


1 Universal indicator/litmus turns purple or blue.


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2 a Carbonate or sulphite.b Test the gas. Carbonates produce carbon dioxide,

which turns limewater milky; sulphites produce sulphur dioxide, which is acidic and has a choking smell.

3 Add barium chloride solution to a solution of each compound and a white precipitate will form. Then add hydrochloric acid: if the precipitate re-dissolves it is a sulphite, if it is unchanged it is a sulphate.

4 Barium sulphite.

5 silver nitrate+lithium bromide silver bromide +lithium nitrateAgNO3(aq)+LiBr(aq) AgBr(s)AgBr(s)+LiNO3(aq)

6 Add acidified silver nitrate solution: if a yellow precipitate is formed, the unknown is copper bromide. Then add barium chloride solution followed by hydrochloric acid: if a white precipitate remains, the precipitate is copper sulphate.

Summary exercise

blue, hydrochloric, sulphur dioxide, red, carbon dioxide, limewater, precipitate, sulphite, silver, cream, iodide

Higher questions

1 a Na2SO3+2HCl 2NaCl+SO2+H2O (bubbles of gas)

b Na2SO3+BaCl2 2NaCl+ BaSO3 (white precipitate)

c AgNO3 + NaBr AgBr+NaNO3 (cream precipitate)

2 Similar: both produce a gas. Different: carbonates produce carbon dioxide, which turns limewater milky; sulphites produce sulphur dioxide, which has a choking smell and is acidic.

Extension questions

1 a It is acidified to remove precipitates of ions such as OH–; CO3

2– and SO32–.

b Test for sulphite, as sulphur dioxide is poisonous.

Worksheet C3.3 5c

1 a magnesium nitrate H(NO3)2+H2Ob nitric acid + potassium sulphite

potassium nitrate+water+sulphur dioxide 2HNO3+K2SO3 2KNO3+H2O+SO2

2 a lithium chloride + barium sulphite LiCl(aq)b potassium sulphate+barium chloride

potassium chloride + barium sulphate K2SO4(aq)+BaCl2(aq) 2KCl(aq)+BaSO4(s)

C3.3 6 Analysis in action


1 They might be asked to analyse: the purity of drinking water, the source of pollution, the contents of consumer products or materials found at a crime scene.

2 Test 1 tells us that the indigestion tablets contain sodium ions and the steriliser contains potassium ions. It tells us nothing about the fertiliser and moss killer.

3 Test 2 tells us that the moss killer contain iron(II) ions and the fertiliser contains ammonium ions. It tells us nothing about the, indigestion tablets and steriliser.

4 Test 3 tells us that the indigestion tablets contain carbonate ions and steriliser contains sulphite ions. It tells us nothing about the fertiliser and moss killer.

5 They don’t contain carbonate or sulphite ions.

6 The moss killer contains chloride ions and the fertiliser contains sulphate ions.

7 Possible chemical contents are: indigestion tablets – calcium carbonate; fertiliser – ammonium; moss killer – iron(II) chloride; and steriliser – potassium sulphite.

Summary exercise

burner, flame, indicator, blue, hydroxide, hydrochloric, chloride, acidified

Higher questions

1 a Add sodium hydroxide solution and heat, if ammonium ions are a present a smelly alkaline gas will be produced (test with moist litmus paper). Add acidified silver nitrate solution, a white precipitate will form if chloride ions are present.

b NH4Cl+NaOH NH3+H2O+NaCl AgNO3+ NaCl AgCl+NaNO3

2 a Testing for preservatives, ion content and additives.

b �easuring levels of sulphur dioxide or nitrogen dioxide in air.

Extension questions

1 Flame test, universal indicator test, sodium hydroxide test, hydrochloric acid test, barium chloride test and acidified silver nitrate test.



Worksheet C3.3 6b

Ion Ionsymbol

Flame test results Universal indicator colour Results of sodium hydroxide test (and secondary tests where necessary)

hydrogen H+ none red no visible effect

sodium Na+ yellow depends on compound no visible effect

potassium K+ lilac depends on compound no visible effect

aluminium Al3+ none depends on compound white precipitate

calcium Ca2+ red depends on compound white precipitate

copper Cu2+ blue depends on compound blue precipitate

iron(II) Fe2+ none depends on compound green precipitate

iron(III) Fe3+ none depends on compound brown precipitate

ammonium NH4+ none depends on compound no visible effect

Ion Ionsymbol

Universal indicator colour

Results of hydrochloric acid test. (and secondary tests where necessary)

Results of acidified silver nitrate test

hydroxide OH– purple/blue no visible effect no visible effect

carbonate CO 2– 3 depends on compound bubbles of gas which turn limewater

milkyno visible effect

sulphite SO 2– 3 depends on compound bubbles of gas which turn moist

universal indicator orange/redno visible effect

sulphate SO 2– 4 depends on compound no visible effect no visible effect

chloride Cl– depends on compound no visible effect white precipitate

bromide Br– depends on compound no visible effect cream precipitate

iodide I– depends on compound no visible effect yellow precipitate

Worksheet C3.3 6c

1 a Carbon dioxide;b potassium carbonate – K2CO3.

2 a Barium sulphate;b iron(II) sulphate – FeSO4.

3 a Silver chloride;b calcium chloride.

4 a Ammonia;b ammonium hydroxide – NH4OH.

5 a Sodium, Iron(III) and bromide;b silver bromide;c barium bromide – BaBr2 and iron(III) bromide

– FeBr3.

C3.3 7 Explaining ion tests with equations


1 a Na+Cl–;b Ca2+(Br–)2;c Fe2+SO 2–

4 ;d Al3+(OH–)2.

2 An ion which is unchanged during a reaction.

3 a Na+(aq) and Cl–(aq);b H+(aq)+OH–(aq) +H2O(l).

4 An equation which only include substances which are changed during a reaction (spectator ions missing).

5 Na+(aq) and Cl–(aq).

6 a Na+(aq) and SO 2– 4 (aq);

b Cu2+(aq)+2OH–(aq) Cu2+(OH–)2(s).

Summary exercise

equations, reactants, symbol, products, formulae, compounds, solid, liquid, spectator ions

Higher questions

1 a Na3Pb �gBr2c CuOd Fe2(SO3)3e Ba(NO3)2f (NH4)2SO4

2 a Li2SO3+2HCl 2LiCl+SO2+H2Ob SO3

2–(aq)+2H+(aq) SO2 (g)+H2O(l)


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Extension questions

1 a Flame test red=lithium ions, blue=copper ions. Add hydrochloric acid and test gas with limewater, milky=carbonate ions. Acidified silver nitrate test, white precipitate=chloride ions.

b 2HCl+CuCO 2– 3 CuCl2+H2O(l)+CO2(g)

balanced formulae equation 2H+(aq)+CO 2–

3 (aq) H2O(l)+CO2(g) ionic equation

AgNO3(aq)+LiCl(aq) AgCl(s)+LiNO3(aq) balanced formulae equation

Ag+(aq) + Cl–(aq) Ag+Cl–(s) ionic equation

Worksheet C3.3 7a

1 Li+ Na+ �g2+ Ca2+ Al3+ K+ F– Cl– O2– S2– P3–

Non-metals

fluorine chlorine oxygen sulphur phosphorus

Met

als

lithium Li+F– Li+Cl– (Li+)2O2– (Li+)2S2– (Li+)3P3–

sodium Na+F– Na+Cl– (Na+)2O2– (Na+)2S2– (Na+)3P3–

magnesium Mg2+(F–)2 Mg2+(Cl–)2 Mg2+O2– Mg2+S2– (�g2+)3(P3–)2

calcium Ca2+(F–)2 Ca2+(Cl–)2 Ca2+O2– Ca2+S2– (Ca2+)3(P3–)2

aluminium Al3+(F–)3 Al3+(Cl–)3 (Al3+)2(O2–)3 (Al3+)2(S2–)3 Al3+P3–

potassium K+F– K+Cl– (K+)2O2– (K+)2S2– (K+)3P3–

2 a �g2+SO 2– 4 b (Al3+)2(CO 2–

3 )3

c K+NO –3 ; d (Na+)2CO 2–

4

e Fe3+(OH–)3 f Ca2+(NO –3 )2

g Cu2+CO 2– 3 h Fe2+(NO –

3 )2

i (Al3+)2(SO 2– 4 )3 j (K+)2SO 2–

3

Worksheet C3.3 7b

1 a Na+Br–(aq)+Ag+NO – 3 (aq) Ag+Br–(s)+

Na+NO – 3 (aq)

b Cream coloured.

2 a Ba2++2Cl–(aq)+2K++SO 2– 3 (aq) 2K++

2Cl–(aq)+Ba2+SO 2– 3 (s)

b Add hydrochloric acid and the barium sulphite precipitate will dissolve.

3 a 2H+(aq)+CO32–(aq) H2O(l)+CO2(g)

Lithium and chloride are the spectator ions.b Limewater turns milky.

4 a �g(s)+(H+)2SO4(aq) �g2+SO 2– 4 (aq)+H2(g)

b �g(s)+2H+(aq)+SO4(aq) �g2+(aq) + SO 2–

4 (aq)+H2(g)c �g(s)+2H+(aq) �g2+(aq)+H2(g) – sulphate is

the spectator ion.

C3.3 8 How much is dissolved?


1 a Qualitative analysis finds out what substances are present, quantitative analysis finds out how much is present;

b g and g dm–3.

2 1.8 g.

3 Volume of solution, mass of dry evaporating basin and mass of evaporating basin+solute.

4 Water used in medicines or pH meters.

5 Water that contains high levels of calcium ions. Soap will not lather in hard water.

6 Weigh a dry evaporating basin.�easure a volume of salt solution.Pour the salt solution into the evaporating basin.Heat to evaporate the water.Weigh the evaporating basin+salt.Calculate the mass of salt left.Calculate the concentration in g dm–.

7 a 0.28g and 280 mg dm–3;b moderately hard; 14 to 20.9.



Summary exercise

quantitative, solute, mass, concentration, solution, evaporating, balance, heat, cool, reweigh

Higher questions

1 a 1.28 g;b 6.5 g.

2 a 2.8 g dm–3;b 2800 mg dm–3.

Extension questions

1 a Increasing the concentration of ethylene glycol increases the freezing point;

b 326 cm3;c it will have a higher freezing point than the

mixture with water.

Worksheet C3.3 8b

1 Sodium chloride.

2 Ionic.

3

Name of salt Formula

sodium chloride NaCl

magnesium sulphate MgSO4

potassium chloride KCl

calcium chloride CaCl2

potassium K2SO4

4 35 g.

5 a 1.068 g;b 2.993 g.

6 3.4 g dm–3.

C3.3 9 Counting formulae


1 a C3H8+5O2 3CO2+4H2Ob 2Al+6HCl 2AlCl3+3H2

2 A molecule containing two atoms only.

3 They have a lattice structure and they don’t form molecules.

4 a Calcium.b 2 times heavier.

5 a 152; b 148.

6 a 44 g; b 96 g.

7 C.

8 The formula mass of a compound is the sum of the relative atomic masses of all the atoms of all the elements in its formula. A mole of a compound is it’s formula mass in grams.

Summary exercise

element, formulae, balanced, calculations, mass, atomic, mole, grams

Higher questions

1 a (NH4)2SO4; b O2; c Pb(NO3)4; d SiO2.

2 a 74; b 292; c 28; d 164.

3 a Fe2O3+3CO 2Fe+3CO2;b 2NH3+3CuO 3Cu+N2+3H2O.

Extension questions

1 a H2SO4+2NaNO3 2HNO3+Na2SO4b sulphuric acid=98, nitric acid=63, sodium

nitrate=85 and sodium sulphate=142;c i 268; ii 268;d they are the same as nothing is lost or gained

(just rearranged).

Worksheet C3.3 9a

Race 1a Fe(s)+I2(g) FeI3(s).b C3H8(g)+O2(g) CO2(g)+H2O(l)c CH4(g)+H2O(g) CO(g)+H2(g)d �g(s)+HBr(aq) H2(g)+�gBr2(aq)e NH3(g)+H2SO4(aq) (NH4)2SO4(aq)

Race 2a 2Rb+Cl2 2RbClb C+O2 CO2c �g+2HF �gF2+H2d 2H2O2 2H2O+O2e CH4+2O2 CO2+2H2O

Race 3a C4H8+6O2 4CO2+4H2Ob 2NaClO3 2NaCl+3 O2c �g+2HCl �gCl2+H2d 2Li+2H2O 2LiOH+H2e C5H12+8O2 5CO2+6H2O

Worksheet C3.3 9b

1 a 58.5; b 95.

2 a 64 g; b 80 g.

3 a 303 g; b 331.

4 a 53.5 g; b 132 g.


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5 D.

6 A.

7 a 2K+Cl2 2KClb Zn+2HF ZnF2+H2c 2H2O2 2H2O+O2d 2H2O+2Na 2NaOH+H2e C6H12+9O2 6H2O+6CO2f 2HCl+Ca H2+CaCl2

C3.3 10 Measuring in moles


1 �etre, kilogram, dozen and ream.

2 a 496 g; b 12.8 g; c 530 g; d 63 g.

3 a 3; b 5; c 0.05; d 0.25.

4 They contain the same number of particles (formula units).

5 A.

6 a 259 g; b 2.2 moles.

7 A mole of all substances contains the same number of formulae units and the mole is useful in calculations in chemistry.

Summary exercise

mole, formula, amounts, number, convert, masses

Higher questions

a 0.00025 moles; b 4500 moles.

2 a 164 g;b 8×6×1023 (4.8×1024);c 820 g;d i 3×6×1023 (1.8×1024); ii 5×3×6×1023 (9×1024).

Extension questions

1 a C; b B; c B; d C.

Worksheet C3.3 10a

1 a 34 g; d 10 g; b 400 g; e 176 g; c 48 g; f 600 g.

2 a 0.5 moles; d 6 moles;b 20 moles; e 0.2 moles;c 0.2 moles; f 0.8 moles.

3 a 23, atoms;b 18, molecules;c 32, molecules;d 80, copper, oxide.

4 a 96 g; d 140 g;b 11.2 g; e 30 g;c 0.56 g; f 171 g.

5 a 0.04 moles; d 0.35 moles;b 0.25 moles; e 2.25 moles;c 0.1 moles; f 0.6 moles.

Worksheet C3.3 10b

1 a 85 g; d 56.8 g;b 285 g; e 380.8 g.c 640 g;

2 a 0.4 moles; d 6 moles;b 0.05 moles; e 0.02 moles.c 0.2 moles;

3 C.

4 B.

5 B.

6 D.

7 D.

C3.3 11 How much reacts?


1 40 g.

2 18.9 g.

3 28.7 g.

4 6 g.

5 The mass of magnesium oxide or the mass of hydrochloric acid reacting.

Summary exercise

product, reaction, calculate, balanced, mole, units, grams, question

Higher questions

1 a 9.56 g;b 3.68 g;c 0.64 g.

2 1888.9 kg.

Extension questions

1 a 142 g;b 196 g;c n=3.



Worksheet C3.3 11b

1 0.25 g.

2 4 g.

3 16 g.

4 13.2 g.

5 2.45 g.

6 2.4 g.

7 1920 g.

8 264 g.

9 150 kg.

10 781.25 g (0.78125 kg).

Worksheet C3.3 11c

1 2.25 g.

2 14 g.

3 4.8 g.

4 5.35 g.

5 1.14 kg.

6 33.6 g.

7 14.6 g.

8 23.53 g.

C3.3 12 Avogadro’s law and gas


1

measuring cylinder

magnesium

hydrochloric acid

2 Equal volumes of gases contain equal numbers of gas particles when measured at the same temperature and pressure.

3 a 400 cm3; b 250 cm3.

4 2000 cm3.

5 The distances between gas molecules are large compared to their molecular sizes and since these distances are similar in all gases the molecular sizes do not effect their overall volume and so the same number of molecules of any gas takes up the same volume.

Summary exercise

law, volumes, numbers, temperature, calculations, gases

Higher questions

1 a CO all used up and O2 in excess;b 80 cm3;c 100 cm3.

2 2000 cm3.

Extension questions

1 a C4H10;b C4H10+6½O2 4CO2 5H2Oc no water (reduced by 100 cm3).

Worksheet C3.3 12a

Part A

1 Equal volumes of gases, at the same temperature and pressure, contain the same number of gas particles (molecules).

2 100 cm3.

3 0.5 dm3.

4 120 cm3.

5 a 50 cm3;b 100 cm3.

6 a 350 cm3;b 200 cm3;c It is a liquid.

7 a 400 cm3;b 200 cm3 carbon dioxide and 400 cm3 water.

Part B

1 a 500 cm3;b 500 cm3;c 300 cm3;d 400 cm3;e 1200 cm3.

2 a 400 cm3;b 400 cm3 oxygen, 800 cm3 carbon dioxide;

and 1600 cm3 of water. Total=2800 cm3.


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Worksheet C3.3 12b

1 temperature, volumes, equal, Avogadro’s

2 60 cm3.

3 200 cm3.

4 250 cm3 oxygen and 500 cm3 sulphur dioxide.

5 a B;b C.

6 24 dm3.

7 a 250 cm3;b 150 cm3.

8 a 10 dm3;b 5 dm3.

9 500 cm3.

10 a 4000 cm3;b 4000 cm3.

11 a 300 cm3;b 200 cm3;c It is a liquid.

3.3.13 Working with gases


1 Any three from: H2, CO, CH4 and H2S.

2 Hydrogen sulphide and carbon monoxide are poisonous and hydrogen and methane are explosive.

3 a 1.33g; b 60 dm3.

4 0.48 dm3.

5 C.

Summary exercise

volume, mole, pressure, molar, calculations, masses, gas

Higher questions

1 a 0.13 g;b i 398,181.8 dm3; ii Trees remove carbon dioxide through

photosynthesis and so help reduce the greenhouse effect which is causing global warming.

2 0.116 g.

Extension questions

1 a 23.33 dm3;b 0.0012 g cm–3;c use a larger syringe or repeat and average.

Worksheet C3.3 13b

1 a 22 g;b 12 dm3;c 24 g;d 6 dm3.

2 D.

3 C.

4 0.117 g.

5 0.478 g.

6 2.4 dm3.

7 a 0.8 g;b 0.242 g;c 4.8 dm3;d 1.2 dm3.

8 C.

Worksheet C3.3 13c

1 a 96 dm3;b 8 dm3;c 4.8 dm3;d 177.5 g.

2 4.8 dm3.

3 2 dm3.

4 a Hydrogen;b methane;c carbon monoxide, 40 cm3 of hydrogen sulphide.

C3.3 14 Looking at solutions


1 Grams per decimetre cubed (g dm–3) or moles per decimetre cubed (mol dm–3).

2 36.5 g dm–3.

3 0.05 mol dm–3.

4 0.16 mol dm–3.

5 C.

6 60 g dm–3 and 1.5 mol dm–3.

Summary exercise

amount, dissolved, solution, grams, moles, decimetre, concentration, number, volume, convert, mass

Higher questions

1 a 34 g dm–3;b 0.85 g.



2 a 82.14 g dm–3 of ammonium sulphate; 25.0 g dm–3 of ammonium carbonate; 21.43 g dm–3 of borax; 21.43 g dm–3 of starch;b 0.63 mol dm–3 of ammonium sulphate – (NH4)2SO4 0.27 mol dm–3 of ammonium carbonate –

(NH4)2CO3 0.106 mol dm–3 of borax – Na2B4O7 0.52 mol dm–3 boric acid – H3BO3;c As there is no set formula for starch.

Extension questions

1 4.17 mol.

2 8.34 mol.

3 8.34 mol dm–3.

4 34 g.

5 283.56 g dm–3.

6 0.834 mol dm–3 and 28.356 g dm–3.

Worksheet C3.3 14a

1 solute, solvent, grams, moles

2 a 2.8 g;b 12 g.

3 a 25.2 g;b 1 g.

4 a 92 g dm–3;b 23.4 g dm–3.

5 a 0.04 mol dm–3;b 0.00625 mol dm–3.

6 a 4 g;b 0.25 mol dm–3.

7 a 80 g;b 360 g dm–3.

Worksheet C3.3 14b

1 96 g.

2 54 g.

3 112 g dm–3.

4 0.1 mol dm–3.

5 a 40 g dm–3; b 0.25 mol dm–3.

6 Bottle C.

C3.3 15 Titration and standard solutions


1 An analysis by measuring the volumes of solutions which react together.

2 a Used to measure varying volumes of a solution added during a titration;

b used to measure a set volume of a solution.

3 Not stable on storage.

4 1.06 g.

5 Fill a burette with the acid, and note first level.�easure a set volume of the alkali using a pipette and pipette filler.Place alkali into a conical flask and add a suitable indicator.Slowly add the acid to the alkali until the indicator just changes colour.Note the final level of acid in the burette and calculate volume added.

Summary exercise

analysis, volumes, titration, pipette, added, indicator, mass, weigh, flask

Higher questions

1 a 11.25 g;b need to know the formula exactly to weigh

out a set number of moles accurately.

2 Fill burette with 0.2 mol dm–3 hydrochloric acid and note first level.�easure 20 cm3 of limewater with a pipette (and pipette filler).Transfer the limewater to conical flask and add suitable indicator.Slowly add the hydrochloric acid to the limewater until indicator just changes colour.Note final volume of hydrochloric acid and calculate volume added.

Extension questions

1 a 12.475 g;b variable formula (amount of water).

2 a 382;b 1.146 g.

Worksheet C3.3 15c

1 a 26.5 g;b 1.4625 g;c 0.79 g.


C3.

3


2 a Stable on storage and reacts completely with the alkali;

b 9.2 g.

3 a Used to accurately measure the volume of acid added during the titration;

b used to accurately measure a fixed volume of alkali.

4 E G A C D F B.

5 The volume of solutions which react together exactly.

6 Burette, filter funnel, pipette, pipette filler, indicator, conical flask, white tile, standard alkali solution.

C3.3 16 Volumetric analysis


1 Any two from: pollutants in water, accuracy of contents, body fluids in medicine and solutions used in industry.

2 26.3 cm3.

3 0.1344 mol dm–3.

4 a 0.005 moles;b 0.037 g;c 0.37 g dm–3.

5 Volume of alkali used; volume of acid needed for neutralisation; concentration of acid used and balanced equation for the reaction between the acid and alkali.

Summary exercise

concentration, alkali, titration, volumes, exactly, balanced, number

Higher questions

1 0.146 mol dm–3.

2 625 cm3.

3 1.14 mol dm–3.

4 5.0 dm3.

Extension questions

1 a Hydrochloric acid in excess;b iron in excess.

Worksheet C3.3 16b

1 0.16 mol dm–3.

2 1.2 mol dm–3.

3 6.25 mol dm–3.

4 0.0023 mol dm–3.

5 25.0 cm3.

6 80.0 cm3.

7 a 14.1 cm3;b 0.71 mol dm–3.

Worksheet C3.3 16c

1 C.

2 a

hydrochloric acid in burette

flask containing sodium hydroxide + indicator

pipette

b phenolphthalein indicator, colour change pink to clear;

c 0.1 mol dm–3.

3 1.5 mol dm–3.

4 0.075 mol dm–3.

5 0.001 mol dm–3.

6 1.424 mol dm–3.

7 12.0 cm3.

8 10.0 dm3.

C3.3 17 Questions


1 a Quantitative analysis finds out how much of a substance is present.

Qualitative analysis finds what substances are present.

A titration measures the volumes of solutions which react together.

b Cations (metals).



2 All ionic compound contain two ions.

3 a Copper hydroxide, blue;b silver bromide, cream.

4 a CaCl2; b BaO; c CaSO4; d Al(OH)3.

5 Sodium sulphite.

6 It contains calcium and/or aluminium ions and contains bromide ions.

7 a 18;; b 32;; c 24;; d 44.

8 a 4 moles;; b 0.2 moles;; c 20 moles;; d 0.25 moles.

9 a 12 dm3; b 2.4 dm3; c 120 dm3; d 8 dm3.

10 11 g dm–3 and 0.301 mol dm–3.

11 a 0.5 moles; b 23.75 g.

12 a Cl–;b Zn(s)+2H+(aq) Zn2+(aq)+H2(g).

13 200 cm3.

14 a The mass of dry evaporating basin empty, the mass of dry evaporating basin and solid and the volume of water evaporated;

b carbonate and calcium ions.

15 2.5 g.

16 a Precipitation;b a positive ion;c copper(II) Cu2+;d by the colour of the precipitate formed;e i Fe(NO3)3(aq).+3NaOH(aq) Fe(OH)3(s)+

3NaNO3(aq) ii brown precipitate formed.

17 a Volumetric analysis: a technique which measures the volumes of solutions which react together.

Standard solution: a solution with an exact known concentration, is stable on storage and reacts completely with the other reactant.

Concentration: a measure of the amount of reactant in a given volume of solution;

b 37.0 cm3;c 1.85 mol dm–3;d i bubbles of gas (solution turns blue); ii H2SO4+CuCO3 CuSO4+H2O+CO2

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