Element and Their Compunds

8/10/2019 Element and Their Compunds

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1.

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se the distributions to e&plain why gases react faster when the temperature is increased.

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(2)(Total 12 marks)

Sri Lankan School 20


21/163

21. This -uestion is about some reactions of halogens and halide ions.

'a) 'i) When chlorine is added to a solution containing bromide or iodide ions, a colourchange occurs. What solvent would you add to the mi&ture to confirm the identityof the halogen produced%

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(1)

'ii) "ive the result for the test with this solvent in a reaction in which bromine is produced.

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(1)

'b) 'i) olid potassium bromide and potassium iodide can be distinguished by theirreactions with concentrated sulfuric acid.

$otassium bromide reacts with concentrated sulfuric acid initially to producehydrogen bromide. This reacts further, as shown below, to produce a sharpsmelling gas and a brown fuming li-uid.

#(!r'g) ( # O / 'l) B O #'g) !r #'l) #( #O'l)

how, by use of o&idation numbers for sulfur, that the sulfuric acid has beenreduced.

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(2)



22/163

'ii) tate TWO observations, which would differ from those with potassium bromide,when potassium iodide reacts with concentrated sulfuric acid.

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(2)

'iii) One product of the reaction with potassium iodide is hydrogen sulfide, ( # . (owdoes this show that iodide ions are more powerful reducing agents than bromideions%

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(1)



23/163

'c) 5n areas where the natural concentration of fluoride ions in rocks is low, some waterauthorities add fluoride to the water supply to improve the dental health of children. Analternative would be to supply free fluoride tablets.

"ive O reason why it could be considered more ethical to supply free fluoride tabletsrather than to add fluoride compounds to the water supply.

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(1)(Total 8 marks)

22. The first five successive ioni0ation energies of an element, X , are shown in the table below.

5oni0ationenergy

first second third fourth fifth

?alue

F k mol 1;

6


24/163

23. Which of the following covalent bonds is the shortest%

A (K=

B (KCl

C (K!r

D (K5

(Total 1 mark)

24. Which pair of atomic numbers represents elements which are both in the p4block of the $eriodic

Table%

A /, 3

B 2, ;#

C 3, ;2

D ;7, #7

(Total 1 mark)

25. The electronic structure of an atom of an element in "roup 2 of the $eriodic Table could be

A ;s # #s # #p#

B ;s # #s # #p /

C ;s # #s # #p2 *s # *p 2 *d 2 /s #

D ;s # #s # #p2 *s # *p 2 *d ;7 /s # /p 2

(Total 1 mark)



25/163

26. Which of the following formulae for compounds of germanium, "e, is unlikely to be correct,given the position of germanium in the $eriodic Table%

A "e= *

B "e #

C "eO #

D "e( /

(Total 1 mark)

27. The electronic configurations of the atoms of four different elements are given below. =or whichelement would you e&pect the value of the first ioni0ation energy to be the largest%

A ;s ;

B ;s #

C ;s # #s ;

D ;s # #s #

(Total 1 mark)

28. Which of the following has the smallest ionic radius%

A = 1

B a

C Mg #

D O#1

(Total 1 mark)



26/163

2 . The graph shows the variation in melting temperatures of the elements across $eriod * ' a toAr) of the $eriodic Table.

'a) Complete the table below to show the type of structure and bonding for the elementsshown.

lement tructure !onding

sodium

silicon

sulfur (3)



27/163

'b) &plain why silicon has a much higher melting temperature than sulfur.

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(2)

'c) &plain why the melting temperature increases from sodium to aluminium.

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(2)



28/163

'd) Magnesium forms the basic o&ide magnesium o&ide, MgO. This o&ide is almost insolublein water. On gentle warming with dilute sulfuric acid, magnesium o&ide reacts to forma-ueous magnesium sulfate solution.

'i) Gescribe how you would use the above reaction to prepare a pure sample ofmagnesium sulfate.

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(5)

'ii) uggest what action should be taken if a pupil spilt a small -uantity of dilutesulfuric acid on a laboratory bench.

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(1)



29/163

'e) The data in the table below will be useful when answering this -uestion.

oluble in water 5nsoluble in water

Mg O / MgCO *rCO *r O /

Magnesium carbonate reacts with dilute sulfuric acid.

MgCO *'s) ( # O / 'a-) B Mg O / 'a-) CO #'g) ( #O'l)

'i) &plain why the reaction between strontium carbonate and dilute sulfuric acidstops after a few seconds.

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(1)

'ii) trontium sulfate is produced when a-ueous sodium sulfate is added to a-ueousstrontium chloride.

"ive the ionic e-uation for the reaction, including state symbols.

(2)(Total 16 marks)

3!. What would be the colour of the solution when iodine is dissolved in a hydrocarbon solvent%

A "rey

B !rown

C Dellow

D $urple

(Total 1 mark)



30/163

31. tarch is often used as an indicator in titrations between sodium thiosulfate and iodine solutions.What colour change would you see at the end4point as sodium thiosulfate is added to iodinesolution in the presence of starch%

A Dellow to colourless

B Colourless to yellow

C !lue4black to colourless

D Colourless to blue4black

(Total 1 mark)

32. Which of the following statements is tr$e %

A Calcium hydro&ide is more soluble in water than magnesium hydro&ide.

B Chlorine is more electronegative than fluorine.

C 5odine is a stronger o&idi0ing agent than bromine.

D The first ioni0ation energy of barium is greater than that of strontium.

(Total 1 mark)

33. 5odine can react with sodium hydro&ide solution to form a5O *'a-), according to the e-uation below.

*5#'a-) 2 aO('a-) B 6 a5'a-) a5O *'a-) *( #O'l)

Which of the statements about the reaction is %alse%

A The o&idation number of some iodine atoms goes up.

B At high temperatures a5O'a-) also forms.

C odium ions are spectator ions.

D The o&idation number of some iodine atoms goes down.

(Total 1 mark)



31/163

34. The graph below shows the boiling temperatures of the hydrides of "roup +.



32/163

'a) 'i) 5dentify the type of intermolecular force that gives rise to the unusually high boiling temperature of hydrogen fluoride.

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(1)

'ii) tate and e&plain whether the electronegativity of fluorine is greater than, similarto or less than, that of bromine.

(ence e&plain why hydrogen fluoride can form the type of intermolecular forcenamed in 'a)'i) but hydrogen bromide cannot.

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(3)

'iii) >se the graph to predict what the boiling temperature of hydrogen fluoride would be without the presence of the type of intermolecular force named in 'a)'i).

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(1)



33/163

'b) $ropanone, C( *COC( *, is a useful solvent for cleaning glassware in laboratories.

'i) Why is propanone able to dissolve a wide range of substances%

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(1)

'ii) $ropanone can be used to remove both water and octane from glassware. =or eachof these substances, identify the strongest intermolecular force formed with

propanone and the feature of the propanone molecule involved.

&ater ................................................................................................................

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(2)(Total 8 marks)



34/163

35. Calcium o&ide, known as -uicklime, is produced by the thermal decomposition of calciumcarbonate, found naturally in limestone.

'a) 'i) &plain what is meant by the term t#ermal "ecom osition .

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(2)

'ii) Write an e-uation for the thermal decomposition of calcium carbonate, includingstate symbols.

(1)

'iii) Other "roup # carbonates can also undergo thermal decomposition. Gescribe and

e&plain the trend in thermal stability of carbonates down "roup #.

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(3)



35/163

'b) 7.;#; g of an impure sample of -uicklime was dissolved in 67.7 cm * of hydrochloricacid, concentration 7.;77 mol dm 1* . The e&cess hydrochloric acid was titrated withsodium hydro&ide solution, concentration 7.;77 mol dm 1*, and ;3.7 cm * was needed to

Lust neutrali0e the acid. The indicator used was methyl orange.

The e-uations for the reactions involved are shown below.

CaO's) #(Cl'a-) B CaCl #'a-) ( #O'l)

(Cl'a-) aO('a-) B aCl'a-) ( #O'l)

'i) What colour would the indicator be at the end4point%

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(1)

'ii) Calculate the number of moles of hydrochloric acid that reacted with the sodiumhydro&ide solution.

(1)

'iii) Calculate the number of moles of hydrochloric acid originally added to the-uicklime. >se this answer and your answer to 'b)'ii) to calculate the number ofmoles of -uicklime that reacted with the hydrochloric acid.

(2)

'iv) Calculate the percentage purity of the sample of -uicklime. "ive your answer tot#ree significant figures.

(2)



36/163

'c) 'i) Gescribe how to carry out a flame test on the impure sample of -uicklime toconfirm that it contains calcium ions.

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(3)

'ii) 5f the flame test gave a green colour, in addition to the e&pected brick red flame,which "roup # metal is also likely to be present%

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(1)(Total 16 marks)

36. 'a) 'i) Complete the electronic configuration of the magnesium atom.

1s2......................................................................................................................

(1)

'ii) Complete the electronic configuration of the chlorine atom.

1s#......................................................................................................................

(1)

'b) 'i) Write the e-uation, including state symbols, for the reaction of magnesium withchlorine.

(2)

'ii) ame the type of bonding present in magnesium chloride.

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(1)

'iii) Graw a diagram 'using dots or crosses) to show the bonding in magnesiumchloride. 5nclude A the electrons in each species and the charges present.



37/163

(3)



38/163

'c) tate the type of bonding that e&ists in solid magnesium.

Type.............................................................................................................................

(1)

'd) &plain fully why the melting temperature of magnesium is higher than that of sodium.

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(3)

(Total 12 marks)

37. 'a) Gefine the term %irst ioni*ation ener+, .

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(3)

'b) Write an e-uation, with state symbols, to illustrate the process occurring when the secon"ioni0ation energy of sodium is measured.

(2)



39/163

'c) The graph below shows the variation in the %irst ioni0ation energies of some of theelements in $eriod *.

=irst ioni0ation

energyFk mol 1;



40/163

'i) On the graph, use crosses to show the appro&imate values of the first ioni0ationenergies for the elements a, $ and .

oin the crosses to complete your graph.

(3)

'ii) &plain why the first ioni0ation energies generally increase across the periodsodium to argon ' a to Ar).

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(3)

'iii) &plain why the first ioni0ation energy of aluminium is less than that of

magnesium.

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(2)



41/163

'd) $lace the following species

- - - /

in order of increasing first ioni0ation energy, starting with the lowest.

:owest first (ighest first

ioni0ation energy ioni0ation energy

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(1)(Total 14 marks)

38. Which of these metal hydro&ides is the most soluble in water%

A !arium hydro&ide

B Calcium hydro&ide

C Magnesium hydro&ide

D trontium hydro&ide

(Total 1 mark)

3 . Which of these metals will give a lilac flame colour%

A odium

B Calcium

C $otassium

D Magnesium

(Total 1 mark)



42/163

4!. Which of these statements about fluorine is not correct%

A 5t is a gaseous element at room temperature and pressure.

B 5t can react with chloride ions to form chlorine.

C 5t forms salts with "roup ; metals.

D 5t is less electronegative than chlorine.

(Total 1 mark)

41. What is the o&idation number of o&ygen in dio&ygen difluoride, O #=#%

A 1;

B 1#

C ;

D #

(Total 1 mark)

42. Which concentrated acid should be used to dissolve a carbonate of a "roup # metal to carry outa flame test%

A ethanoic acid

B hydrochloric acid

C nitric acid

D sulfuric acid

(Total 1 mark)



43/163

43. What colour does a barium salt give in a flame test%

A colourless

B green

C red

D yellow4red

(Total 1 mark)

44. eparate flame tests are carried out with lithium, sodium, potassium, magnesium, calcium and

strontium salts. (ow many of these metal ions would colour the flame red%

A ;

B #

C *

D /

(Total 1 mark)

45. A "roup # element reacts vigorously with water to produce a soluble hydro&ide, which forms awhite precipitate when neutralised by sulfuric acid and forms a carbonate which is very stable toheat. The element could be

A magnesium

B calcium

C strontium

D barium

(Total 1 mark)



44/163

46. The "roup # metals, considered in order of increasing atomic number, show a "ecrease in

A first ionisation energy

B nuclear charge

C chemical reactivity

D ionic radius

(Total 1 mark)

47. When a "roup ; metal nitrate is heated, brown fumes are observed. The metal could be

A lithium

B sodium

C rubidium

D caesium

(Total 1 mark)

48. Which of the following statements is =A: %

A iodine is more electronegative than bromine.

B fluorine is more electronegative than chlorine.

C metallic elements tend to react by loss of electrons.

D chlorine is more electronegative than sulfur.

(Total 1 mark)



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46/163

'iii) >se your answer to 'ii) to calculate the number of moles of iodine which reacted.

(1)

'iv) Geduce the concentration of chlorine, in mol dm 1*, in the swimming pool water.

(1)

'b) The disinfecting action of chlorine in swimming pools is due to the presence of chloric'5)acid, (ClO, formed by the reaction of chlorine with water.

5n many swimming pools, chemicals other than chlorine are used to form chloric'5) acid.This is partly because the use of chlorine gas causes much more corrosion of metal partsin swimming pools than does chloric'5) acid.

Compounds used to chlorinate swimming pool water in this way include calciumchlorate'5) and chlorine dio&ide.

'i) tate and e&plain the type of reaction that occurs when chlorine attacks a metal,using the e&ample of iron.

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(2)

'ii) uggest one other reason why the use of chlorine is undesirable in swimming pools.

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(1)

'iii) "ive the formula for calcium chlorate'5).

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47/163

(1)



48/163

'iv) Chlorine dio&ide, ClO #, undergoes a disproportionation reaction when it reactswith water.

/ClO # #( #O (ClO *(ClO *

&plain, in terms of o&idation numbers, why this is a disproportionation reaction.

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(2)



49/163

'c) Giscuss and e&plain the science communityHs advice that C=Cs should no longer be usedin aerosols, foams and refrigerants. upport your answer with one or more e-uations.

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(6)(Total 17 marks)



50/163

5!. 'a) The graph below shows the first ionisation energies of the elements :i, !e, and !.

Complete the graph by adding the a ro0imate first ionisation energies of the elementsC to e.

, n e r g y

: i ! e ! C . O = . e, l e m e n t s

= i r s t i o n i s a t i o n e n e r g y o f t h e e l e m e n t s : i t o . e

(2)



51/163

'b) &plain why the general trend is for the first ionisation energy to increase across the period.

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(3)

'c) &plain why the first ionisation energy of boron, !, is lower than that of beryllium, !e.

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(2)(Total 7 marks)



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51. 'a) tate the flame colours of

'i) barium

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(1)

'ii) strontium

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(1)

'b) When barium is burnt in e&cess o&ygen a compound containing 3;.;E barium and ;3.


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54/163

'iii) What would be the effect of adding a piece of blue litmus paper and a piece of redlitmus paper to the a-ueous product of the reaction in 'ii)%

Ned litmus .........................................................................................................

!lue litmus ........................................................................................................

(1)(Total 8 marks)

52. 'a) Write the e-uations to show the action of heat on the following solid nitrates. tatesymbols are not re-uired.

'i) lithium nitrate, :i O *.

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(2)

' ii) caesium nitrate, Cs O *.

...........................................................................................................................

(1)

'b) The solubilities of the sulphates and hydro&ides of calcium and barium are shown below.>se the information in t#e ta le to answer the -uestions that follow.

ubstance olubility ubstance olubility

Ca O / slightly soluble Ca'O() # slightly soluble

!a O / insoluble !a'O() # soluble



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'i) !oth calcium and barium metals react with water to give the metal hydro&ide andhydrogen gas.

What "i%%erencewould you e&pect to see after calcium metal and barium metalhave reacted with water%

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(2)

'ii) The reaction between barium metal and e&cess dilute sulphuric acid stops after avery short time. uggest an e&planation for this.

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(2)

'c) uggest the solubility in water of radium sulphate. $ut a cross ' ) in the correct bo&.

A ?ery soluble

B oluble

C lightly soluble

D 5nsoluble

(1)



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'd) Write the ionic e-uation for the reaction of calcium metal with dilute hydrochloric acid.5nclude state symbols in your e-uation.

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(2)(Total 1! marks)

53. 'a) Gefine re"$ction in terms of change in o&idation number.

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(1)

'b) The reaction between solid sodium halides and concentrated sulphuric acid changes as thegroup is descended.

'i) Complete the balancing of the e-uation for the reaction of so"i$m romi"e withconcentrated sulphuric acid.

aCl ( # O / B a( O / (Cl

2 aBr 2-' 4 B a -' 4 -' 2 Br 2 2'

3 a5


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'iii) >se the c#an+es in o&idation number of s$l #$r in the reactions in 'i) to show thatthe halides become more powerful reducing agents as the group is descended.

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(2)(Total 6 marks)

54. 'i) Gefine the term ent#al , o% #,"ration , H #," , of an ion.

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(2)



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'ii) The table below gives some information about the sulphates of the "roup # elementsmagnesium and barium.

s$l #ate lattice ener+,

k mol /1

#,"rationent#al , o% cation

k mol /1

sol$ ilit,

mol "m /3

Mg O / 1#3+/ 1;


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'ii) What is the meaning of the symbol %

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(1)

'iii) &plain, using o&idation numbers, why this reaction is known asdisproportionation.

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(2)

'iv) Write the ionic e-uation, including state symbols, for the reaction of chlorine gaswith bromide ions.

(2)



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'b) 5n the second step, air is blown through the reaction mi&ture to remove the bromine as avapour which is then mi&ed with sulphur dio&ide gas and water vapour.

The unbalanced e-uation for this reaction is !r # ( #O O # B ( !r P O /

#1

'i) 5dentify the elements which are o&idised and reduced and give their o&idationnumbers.

lement o0i"ise" ........................

O&idation number initial ........................ final ........................

lement re"$ce" ........................

O&idation number initial ........................ final ........................

(2)

'ii) >sing this information, or otherwise, balance the e-uation.

!r # ( #O O # B ( !r P O /

#1

(1)(Total 1! marks)

56. 'a) Complete and balance an e-uation for each of the following reactions. Go not includestate symbols.

'i) !a ( #O B ...............................................

(1)

'iii) aCl ( # O / B ...............................................

(1)

'b) tate the flame colours produced by compounds of

'i) barium .................................................................................

(1)

'ii) lithium ................................................................................

(1)



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'c) &plain how compounds of elements in "roups ; and # produce colours in the flame test.

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(3)

'd) When potassium is burnt in e&cess o&ygen, a compound is produced that contains 6/.< E potassium.

Calculate the percentage of o&ygen present and hence calculate the empirical formula ofthis compound.

(3)(Total 1! marks)

57. 'a) (ydrogen chloride can be prepared by reacting concentrated sulphuric acid with solidsodium chloride.

Write an e-uation for the reaction which occurs. tate symbols are not re-uired.

(2)



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'b) When concentrated sulphuric acid is added to solid sodium bromide, the products of thereaction include sulphur dio&ide and bromine.

#( # O / # a!r B !r # O # #( #O a# O /

ulphur and bromine change o&idation number in this reaction.

'i) Write the o&idation numbers at the start and the end of the reaction.

ulphur changes from ..................... to .....................

(1)

!romine changes from ..................... to .....................

(1)

'ii) &plain why the numbers in the balanced e-uation are consistent with the changesin o&idation number.

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(2)

'c) The boiling points of three hydrogen halides are shown below

(ydrogen halide !oiling pointFQ

(ydrogen chloride ;33

(ydrogen bromide #72

(ydrogen iodide #*3



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'i) &plain the trend in boiling point of the three hydrogen halides.

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(2)

'ii) $redict a value for the boiling point of hydrogen fluoride. &plain your reason forchoosing this value.

$redicted value ......................................

&planation

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(3)(Total 11 marks)

58. =lame tests were performed on the following compounds of calcium and sodium.

'i) tate the flame colour in each case

calcium hydro&ide ......................................................................................................

sodium hydro&ide .......................................................................................................

(2)



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'ii) &plain the origin of the colours obtained in flame tests.

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(3)(Total 5 marks)

5 . 'a) Complete the following electronic configurations.

i

*d /s

R Ar S

i 2

*d /s

R Ar S

(2)

'b) &plain why nickel is classified as a transition metal .

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(1)

'c) Consider the following reaction scheme.

- t e ( 1 8 ## 2 p a l e g r e e n p r e c i p i t a t e

a f e w d r o p so f . ( ' a - )*

- t e ( 2 8 p a l e g r e e n p r e c i p i t a t e

R . i ' ( O ) S ' a - )

b l u e s o l u t i o nX

e & c e s s . ( ' a - )*



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'i) What t, es of bond are present in the R i'( #O)2S# ion%

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(2)

'ii) Write an e-uation for the formation of the pale green precipitate.

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(1)

'iii) &plain why -te 1 is a "e rotonation reaction.

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(2)

'iv) ame the type of reaction occurring in -te 2 .

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(1)

'v) "ive an e-uation for the reaction in -te 2 .

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(2)



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'd) &plain why the he&aa-uanickel'55) ion, R i'( #O)2S# , is coloured.

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(3)(Total 14 marks)

6!. 5ron is produced from the ore haematite, which contains iron'555) o&ide.

ome standard enthalpies of formation are given below.

Com o$n" 9 H % : k mol /1

=e#O* 's) 13##

CO 'g) 1;;7CO # 'g) 1*


67/163

'a) 'i) Write the e-uation for the complete reduction of iron'555) o&ide by carbonmono&ide.

Calculate the enthalpy change for this reaction.

(3)

'ii) 5ron'555) o&ide can also be reduced by carbon.

=e#O* *C B #=e *CO H U J /


68/163

'b) On heating, the following e&othermic reaction occurs

*=e's) /( #O'g) =e *O / 's) /( #'g)

At 277 8C, a mi&ture of iron and steam is allowed to reach e-uilibrium. The e-uilibrium partial pressures of hydrogen and steam are ;.2 atm and ;.# atm respectively.

'i) Write the e&pression for the e-uilibrium constant, K p, for the reaction. Calculate itsvalue and state the units.

(2)

'ii) tate the effect, if any, on the value of K p when the temperature is increased.ustify your answer.

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(2)



69/163

'c) When an iron nail is left in a test tube of water containing a little phenolphthalein, it startsto react and region X becomes pink, due to the formation of O( 1 ions.

X

;

seo&idation numbers to e&plain the meaning of the term disproportionation in this reaction.

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(3)



80/163

'b) Gomestic bleaches are dilute solutions of sodium chlorate'5). The amount of ClO 1 ions ina sample can be found by reacting it with e&cess acidified potassium iodide solution.

ClO 1 #5 1 #( 5# + Cl 1 ( #O

The iodine produced is then titrated with standard sodium thiosulphate solution.

;7.7 cm * of a domestic bleach was pipetted into a #67 cm * volumetric flask and madeup to the mark with distilled water.

A #6.7 cm * portion of the solution was added to e&cess acidified potassium iodidesolution in a conical flask.

This mi&ture was titrated with 7.;77 mol dm 1* sodium thiosulphate solution, usingstarch indicator added near the end point.

The mean titre was ;#.67 cm *.

'i) "ive the colour change you would see at the end point.

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(1)



81/163

'ii) The e-uation for the reaction between iodine and thiosulphate ions is

# #O*#1 5 # / O2

#1 #5 1

Calculate the amount 'moles) of chlorate'5) ions in ;.77 dm*

of the ori+inal bleach.

(5)

'iii) >se the e-uation below to calculate the mass of chlorine available from ;.77 dm * of the ori+inal bleach. "ive your answer to * significant figures.

ClO 1 Cl 1 #( Cl# ( #O

(1)



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'c) odium thiosulphate can be used to remove the e&cess chlorine from bleached fabrics.

#O*#1 /Cl # 6( #O # O /

#1 ;7( 3Cl 1

!y considering the change in o&idation number of sulphur, e&plain whether chlorine oriodine is the stronger o&idising agent when reacted with thiosulphate ions.

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(2)

'd) tarch4iodide paper can be used to test for chlorine. 5t contains starch and potassiumiodide.

&plain the reactions taking place when a piece of damp starch4iodide paper is put in agas Lar of chlorine. tate what you would see.

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(2)(Total 14 marks)



83/163

66. 'a) An atom of argon has mass number /7. Complete the table below showing thecomposition of this argon atom.

>se the $eriodic Table as a source of data.

$rotons

lectrons

eutrons

(2)

'b) An atom of potassium has mass number *


84/163

'd) Write the electron configuration of argon in s, p notation.

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(1)

'e) The chart shows the first ionisation energy of some elements in the third period of the$eriodic Table.

= =

==

# 7 7 7

; 6 7 7

; 7 7 7

6 7 7

7$ C l A r Q

; s ti o n i s a t i o ne n e r g yF k m o l 1 ;

'i) Write the chemical e-uation, with state symbols, which corresponds to the firstionisation energy of argon.

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(1)

'ii) On the chart, add a cross to show the first ionisation energy of potassium. ustifyyour choice of the position of the cross.

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(2)



85/163

'iii) &plain why there is a small decrease in first ionisation energy going from phosphorus to sulphur.

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(2)

'iv) &plain why there is an increase in first ionisation energy going from sulphur tochlorine.

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(2)

'f) uggest why argon is used to fill some types of light bulbs.

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(1)(Total 14 marks)

67. Magnesium o&ide is a basic o&ide which produces an alkaline solution with water. Write ane-uation to show how the o&ide ion, O #1 , acts as a base in the reaction with water.

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(Total 1 mark)



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87/163

68. 'a) Complete the following table.

lement $hysical state at roomtemperature Colour

chlorine

bromine

iodine

(3)

'b) 'i) Write the e-uation for the reaction between concentrated sulphuric acid and solid potassium chloride, QCl.

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(1)

'ii) When potassium bromide, Q!r, reacts with concentrated sulphuric acid, bromineand sulphur dio&ide are produced.

"ive the o&idation numbers of bromine and sulphur in the reactants and products.(ence identify the o&idising agent, giving a reason for your choice.

Q!r ................. ( # O / .................

!r # ................. O # .................

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(4)(Total 8 marks)



88/163

6 . 'a) 'i) $otassium supero&ide contains 6/.< E potassium by mass.how that the empirical formula of this compound is QO #.

(3)

'ii) "ive the o&idation number of o&ygen in the compound QO #.

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(1)



89/163

'b) Which of potassium nitrate or lithium nitrate has the higher thermal stability%&plain your answer.

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(3)(Total 7 marks)

7!. 'a) 'i) "ive the electronic configuration of

=e RArS.................................................................................................

=e# RArS.................................................................................................

(2)

'ii) Graw the structure of the he&aa-uairon'55) ion, R=e'( #O)2S# , so as to clearly show

its shape.

(1)



90/163


91/163

'ii) &plain, with the aid of an e-uation, why the value of E U suggests that iron willreact with an a-ueous solution of an acid to give =e # ions and hydrogen gas.

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(3)

'iii) tate why E U values cannot predict that a reaction will occur, only that it is possible.

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(1)

'c) >se the following standard electrode potentials to e&plain why iron'555) iodide does not e&ist in a-ueous solution.

=e* e 1 =e # E U J 7.++ ?

5# #e 1 #5 1 E U J 7.6/ ?

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(2)

(Total 15 marks)


8/10/2019 Element an

Element and Their Compunds

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