10

91

01

00

01ADDITIONAL MATERIALS

In addition to this examination paper, you will need a:• calculator;• copyofthePeriodic Table supplied by WJEC. Refertoitforanyrelative atomic masses you require.

INSTRUCTIONS TO CANDIDATES

Useblackinkorblackball-pointpen.Donotusegelpenorcorrectionfluid.Writeyourname,centrenumberandcandidatenumberinthespacesatthetopofthispage.Section A Answer allquestionsinthespacesprovided.Section B Answer allquestionsinthespacesprovided.Candidatesareadvised toallocate their timeappropriatelybetweenSection A (10 marks) and Section B (70 marks).

INFORMATION FOR CANDIDATES

Thenumberofmarksisgiveninbracketsattheendofeachquestionorpart-question.Themaximummarkforthispaperis80.Youranswersmustberelevantandmustmakefulluseoftheinformationgiventobeawardedfullmarksforaquestion.The QWC label alongsideparticular part-questions indicates thosewhere theQuality ofWrittenCommunicationisassessed.Ifyourunoutofspace,usetheadditionalpage(s)atthebackofthebooklet,takingcaretonumberthequestion(s)correctly.

SM*(S14-1091-01)

Surname

Other Names

CandidateNumber

2

CentreNumber

© WJEC CBAC Ltd.

GCE AS/A level

1091/01

CHEMISTRY – CH1

A.M.FRIDAY,23May2014

1hour30minutes

For Examiner’s use only

Question MaximumMark

MarkAwarded

Section A 1. to 7. 10

Section B 8. 14

9. 11

10. 14

11. 17

12. 14

Total 80

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SECTION A

Answer all questions in the spaces provided.

1. CompletetheelectronicstructureforthesulfideionpresentinNa2S. [1]

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

2. Whichisotopeisthestandardusedindefiningrelativeatomicmasses? [1]

3. State oneexampleofanindustriallyorenvironmentallyimportantheterogeneouscatalyst.Youshouldidentifythereactioncatalysedandnamethecatalyst. [1]

4. HydratedsodiumcarbonatehastheformulaNa2CO3.10H2O.

(a) Calculatetherelativemolecularmass(Mr ) of Na2CO3.10H2O. [1]

Mr = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) Calculate the mass of Na2CO3.10H2O needed to make 250cm3 of a 0.10 mol dm−3 solution. [1]

Mass = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .g

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010003

3Examiner

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© WJEC CBAC Ltd.

238

92U

5. Usetheenergycycletocalculatetheenthalpychangeofformationofcarbonmonoxide. [1]

C(s) + O2(g) CO(g)

Enthalpy change of formation = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .kJmol−1

6. Completetheequationtoshowthetwo-stageprocessbywhicharadioactiveisotopeofuraniumdecays. [2]

12

−394kJmol−1 −284kJmol−1

CO2(g)

lossof42

He2+ lossof 0−1e

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© WJEC CBAC Ltd.

7. Thediagramsshowtheenergydistributioncurveforgaseousmoleculesatafixedtemperature.

(a) Onthediagrambelow,Ea1showstheactivationenergyofaparticularreactionwithoutacatalyst.Indicateonthediagramthefractionofmoleculesthatreact. [1]

(b) Indicateonthediagrambelowtheactivationenergy,Ea2,andthefractionofmoleculesthatreactwhenthereactionproceedswithacatalyst. [1]

Section A Total [10]

Fractionofmoleculeswithenergy,E

energyE

Fractionofmoleculeswithenergy,E

energyE

Ea1

Ea1

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SECTION B

Answer all questions in the spaces provided.

8. (a) Hydrogenexistsasthreeisotopeswithrelativemassesof1,2and3.

Statethesimilaritiesanddifferencesinthecompositionofthesespecificisotopes. [2]

(b) Thefirsttwoelectronicenergylevelsinahydrogenatomareshownonthediagram.

© WJEC CBAC Ltd.

n = ∞

n = 2

n = 1

(i) Completethediagramtoshowenergylevelsn=3,n=4andn=5. [1]

(ii) Markwithanarrowtheenergychangecorrespondingtotheionisationenergyofhydrogen. [2]

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01

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07

7Examiner

only (c) AstudentsaidthattheionisationenergyofhydrogencouldbecalculatedusingtheBalmer

Seriesoflines.

(i) InwhichpartoftheelectromagneticspectrumdoestheBalmerSeriesappear?[1]

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

(ii) Explainwhetherornotthisstudentwascorrect. [2]

(d) Thediagramshowspartofaplotofthefirstionisationenergyofelementsagainsttheiratomicnumbers.LettersQ–T do notrepresentthesymbolsoftheelements.

© WJEC CBAC Ltd.

(i) WritetheequationforthechangeoccurringforthefirstionisationenergyofelementQ. [1]

(ii) InwhichgroupofthePeriodicTableiselementR found? [1]

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

(iii) ExplainwhythefirstionisationenergyofSisgreaterthanthatofT. [3] QWC [1]

Total[14]

First ionisation energy/kJmol−1

Atomicnumberofelement

Q R

S

T

8

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9. Thediagramshowstheprincipalpartsinonetypeofmassspectrometer.

© WJEC CBAC Ltd.

chargedplatestoaccelerateions

electromagnet

slit

detector

electronguntocauseionisation

vaporisedsample

(a) (i) The line labelledX shows the path of ionX passing through the slit and beingdetected.

Ion Y hasahighermasstochargeratiothanionX.DrawalineonthediagramtoshowthepathofionY. [1]

(ii) Withoutalteringtheshapeofthemassspectrometer,whatchangecouldbemadeto allow ion Y,withitshighermasstochargeratio,topassthroughtheslitandbedetected? [1]

X

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09

9Examiner

only (b) Thediagramshowsanincompletemassspectrumforasampleofchlorine,Cl2.

© WJEC CBAC Ltd.

40 60 8050 70

Intensity

m/z

(i) Whationisresponsibleforthepeakatm/z=74?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [2]

(ii) Drawonthespectrumanotherpeakthatyouwouldexpecttosee.Youshouldshowthemasstochargeratioatwhichyouwouldseethepeakand theheightofthepeak. [2]

(c) AcompoundZcontainsonlycarbon,hydrogenandchlorine.Itisanalysedandfoundtocontain10.04%carbonand89.12%chlorinebymass.

(i) FindtheempiricalformulaofcompoundZ. [3]

Empirical formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) WhatotherinformationwouldyouneedtodecidewhetherthisempiricalformulaisalsothemolecularformulaofZ? [1]

(iii) Whatfeatureofamassspectrumgivestheinformationneededinpart(ii)? [1]

Total [11]

10

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10. Thedecompositionofdinitrogen(IV)oxideintonitrogen(IV)oxideisareversiblereactionthatestablishesadynamicequilibrium.

N2O4(g) a 2NO2(g) ∆H=+57kJmol−1

paleyellow darkbrown

(a) Statethemeaningofthetermdynamic equilibrium. [1]

(b) Theconditionsappliedtoanequilibriummixtureofdinitrogen(IV)oxideandnitrogen(IV)oxidewerechanged.Foreachof the following,statewhatwasseen and explain any changethatoccurred. [5]

Temperature increased

Pressure increased

A catalyst was added

© WJEC CBAC Ltd.

(1091-01) Turn over.

11Examiner

only (c) Hydrazine, N2H4, is an unstable liquid that decomposes according to the following

equation.

N2H4(I) N2(g) + 2H2(g)

(i) Calculatethevolumeofgasthatcouldbeobtainedfrom14kgofhydrazine. Assumethatthevolumeof1molofgasis24.0dm3. [3]

Volume of gas = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . dm3

(ii) Oneuseofhydrazineisasafuelinrockets.Apartfromanyenergychanges,stateonefeatureofthisreactionthatsuggestsitwouldbeusefulinrocketpropulsion.

[1]

(d) Nitrogen(IV)oxidereactswithwater.

H2O + 2NO2 HNO2 + HNO3

Bothnitric(III)acid,HNO2,andnitric(V)acid,HNO3,aredescribedasbeingacids.

(i) Defineanacid. [1]

(ii) Completetheequationtoshownitric(III)acidbehavingasanacid. [1]

HNO2 + H2O

(iii) When concentrated nitric(V) acid is mixed with concentrated sulfuric acid thereactionshownbelowoccurs.

HNO3 + H2SO4 H2NO3+ + HSO4

−

Explainthisreactionintermsofacid-basebehaviour. [2]

Total[14]

© WJEC CBAC Ltd.

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11. (a) Ethanol, C2H5OH,isaliquidatroomtemperature.Itisbeingincreasinglyusedasafuel.

(i) Writetheequationthatrepresentsthestandardmolarenthalpychangeofformation(∆Hf) ofethanol. [1]

(ii) Suggestwhythisenthalpychangecannotbemeasureddirectly. [1]

(b) Enthalpychangesofcombustioncanoftenbemeasureddirectly.Theequationfor thereaction which represents the enthalpy change of combustion (∆Hc) of ethanol is asfollows.

C2H5OH(I) + 3O2(g) 2CO2(g) + 3H2O(I)

Astudentusedtheapparatusbelowtodeterminetheenthalpychangeofcombustionofethanol.

© WJEC CBAC Ltd.

calorimeter water

wick

ethanol

Thestudentobtainedthefollowingresults.

Massofspiritburner+ethanolatstart = 72.27g Massofspiritburner+ethanolaftercombustion = 71.46g Temperatureofwateratstart = 21.5°C Temperatureofwateraftercombustion = 75.5°C Volumeofwaterincalorimeter = 100cm3

Theenergyreleasedintheexperimentcanbecalculatedusingtheformula

energyreleased = mc∆T

where m = massofthewateringrams(assume1cm3hasamassof1g) c = 4.2Jg−1°C−1 ∆T= changeintemperatureofthewater

(1091-01) Turn over.

13Examiner

only (i) Calculatetheenergyreleasedintheexperiment. [1]

Energy released = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J

(ii) Theenthalpychangeofcombustionofethanolisdefinedastheenergychangepermolofethanolburned.

Useyouranswerto(i)tocalculatetheenthalpychangeofcombustionofethanol.Give your answer in kJmol−1 and correct to3 significant figures. Include thesign. [3]

∆Hc of ethanol = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . kJmol−1

(c) Anotherstudentdidnotcarryoutanexperimenttofind∆Hcofethanol.Helookeduptheliteraturevalueonarespectedinternetsite.

How would you expect the numerical values obtained by the two students to differ?Explain your answer.

Youmayassumethatbothvalueswerefoundunderthesameconditionsoftemperatureand pressure. [2]

© WJEC CBAC Ltd.

sign value

14

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(d) Thestudentsthenusedtheapparatusfrom(b)tofindtheenthalpychangeofcombustionof higher relativemolecularmassalcohols.They found that as thenumberof carbonatomsincreasedthevalueoftheenthalpychangeofcombustionbecamemorenegative.

(i) Write the equation for the reaction which represents the enthalpy change ofcombustionofpropanol,C3H7OH. [1]

(ii) In terms of bond strengths, explain why enthalpy changes of combustion arenegative. [1]

(iii) Explainwhytheenthalpychangeofcombustionofpropanolismorenegativethanthatofethanol. [1]

(e) Recentresearchhasbeencarriedouttofindeconomicandenvironmentallyfriendlyusesforwastestrawandwoodchippings.

Theprocessofgasificationinvolvesthematerialbeingpartlycombustedatatemperatureofabout700°Ctogiveamixtureconsistingmainlyofhydrogenandcarbonmonoxidebutalsosomecarbondioxide.

Another approach has been to use enzyme catalysed reactions to change thewastematerialintoglucoseandthentoethanol.

Comment on the economic and environmental factors involved in both of theseprocesses. [4]

QWC [2]

Total [17]

© WJEC CBAC Ltd.

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© WJEC CBAC Ltd.

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16Examiner

only12. Hydromagnesiteisamixtureofmagnesiumcarbonateandsolubleimpurities.Astudentcrushed

somehydromagnesiteandaddedasampleofmass0.889gtoexcessdilutehydrochloricacidsothatthemagnesiumcarbonatecomponentreactedfully.

(a) Explainwhytherockwascrushedbeforebeingaddedtotheacid. [1]

(b) Writetheequationforthereactionbetweenmagnesiumcarbonateanddilutehydrochloricacid. [1]

(c) Thegas formedwascollected inagassyringeand its volumewasmeasuredoveraperiodoftime.Thevolumesandtimeswereplotted.Thevolumeof1molofgasundertheseconditionsis24.0dm3.

© WJEC CBAC Ltd.

00

100

50

200

150

5 10 15 20 25 30

Describewhathappenedtotherateofthereactionoverthe30minuteperiod. Explainwhyanychangesintherateoccurred. [3]

VolumeCO2/cm3

Time / minutes

Turn over.

17

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Examineronly

(d) Otherthanbyusinganindicator,howwouldthestudentknowthathydrochloricacidwasinexcess? [1]

(e) (i) Usethegraphtocalculatehowmanymolesofmagnesiumcarbonatereactedwiththehydrochloricacid. [2]

Number of moles MgCO3 = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . mol

(ii) Findthemassofmagnesiumcarbonatethatreactedandhencethepercentageofmagnesiumcarbonatepresentinhydromagnesite. [2]

Percentage of magnesium carbonate = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . %

© WJEC CBAC Ltd.

(1091-01)

18Examiner

only (f) Astudentwantedtocarryoutthisexperimentonanothersampleofhydromagnesite.He

didnothaveagassyringeandthereforehedecidedtocollectthecarbondioxideoverwaterinameasuringcylinder.

© WJEC CBAC Ltd.

Explainwhateffectthiswouldhaveontheresultsoftheexperiment.Youshouldassumethatthegassyringeandthemeasuringcylindercanbothbereadtothesameprecision. [2]

(g) Whenmagnesiumcarbonate isheated itdecomposes tomakemagnesiumoxideandcarbondioxide.

MgCO3(s) MgO(s) + CO2(g)

Magnesiumoxidehasaveryhighmeltingtemperatureandsocanbeusedtolinefurnaces.

What is the atom economy for the production of magnesium oxide frommagnesiumcarbonate? [2]

Atom economy = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . %

Total[14]

Section B Total [70]

END OF PAPER

carbondioxide

water

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Questionnumber

Additional page, if required.Write the question number(s) in the left-hand margin.

© WJEC CBAC Ltd.

Questionnumber

Additional page, if required.Write the question number(s) in the left-hand margin.

Examineronly

(1091-01)

20

© WJEC CBAC Ltd.

SM*(S14-1091-01A)© WJEC CBAC Ltd.

GCE AS/A level

1091/01-A

CHEMISTRY – PERIODIC TABLEFOR USE WITH CH1

A.M. FRIDAY, 23 May 2014

(1091-01A)

2

6.94 Li

Lith

ium

3

9.01 Be

Bery

llium

4

10.8 B

Bor

on 5

12.0 C

Car

bon

6

14.0 N

Nitro

gen

7

16.0 O

Oxy

gen

8

19.0 F

Fluo

rine

9

20.2

Ne

Neo

n10

23.0

Na

Sod

ium

11

24.3

Mg

Magn

esium

12

27.0 Al

Alumi

nium

13

28.1 Si

Sili

con

14

31.0 P

Phos

phoru

s15

32.1 S

Sulfu

r16

35.5 Cl

Chlo

rine

17

40.0 Ar

Arg

on18

39.1 K

Potas

sium

19

40.1

Ca

Cal

cium

20

45.0

ScSc

andiu

m21

47.9 Ti

Tita

nium

22

50.9 V

Vana

dium

23

52.0 Cr

Chrom

ium24

54.9

Mn

Mang

anes

e25

55.8

Fe Iron

26

58.9

Co

Cob

alt

27

58.7 Ni

Nic

kel

28

63.5

Cu

Cop

per

29

65.4

Zn Zinc 30

69.7

Ga

Gal

lium

31

72.6

Ge

Germ

anium

32

74.9 As

Ars

enic

33

79.0

SeSe

leniu

m34

79.9 Br

Brom

ine

35

83.8 Kr

Kryp

ton

36

85.5

Rb

Rubid

ium37

87.6 Sr

Stro

ntium

38

88.9 Y

Yttri

um39

91.2 Zr

Zirco

nium

40

92.9

Nb

Niob

ium

41

95.9

Mo

Molyb

denum

42

98.9 Tc

Tech

netiu

m43

101

Ru

Ruthe

nium

44

103

Rh

Rhod

ium45

106

PdPa

lladiu

m46

108

Ag Silv

er47

112

Cd

Cadm

ium48

115 In

Indi

um49

119

Sn Tin

50

122

SbAn

timon

y51

128

TeTe

lluriu

m52

127 I

Iodi

ne53

131

XeXe

non

54

133

Cs

Caes

ium

55

137

BaB

ariu

m56

139

LaLa

nthan

um57

179

Hf

Hafn

ium

72

181

TaTa

ntalu

m73

184

WTu

ngste

n74

186

Re

Rhen

ium75

190

Os

Osm

ium

76

192 Ir

Iridi

um77

195

Pt

Plat

inum

78

197

Au Gol

d79

201

Hg

Mer

cury

80

204 Tl

Thall

ium81

207

Pb Lead 82

209 Bi

Bism

uth

83

(210

)Po

Polon

ium84

(210

)At

Asta

tine

85

(222

)R

nR

adon

86

(223

)Fr

Fran

cium

87

(226

)R

aR

adiu

m88

(227

)Ac

Actin

ium89

THE

PER

IOD

IC T

AB

LE1

2 G

roup

34

56

70

1 2 3 4 5 6 7

‣ ‣‣

1.01 H

Hydr

ogen

1

4.00 He

Heliu

m2

d B

lock

s B

lock

Perio

d

p B

lock

140

Ce

Cer

ium

58

141 Pr

Pras

eody

mium

59

144

Nd

Neod

ymiu

m60

(147

)Pm

Prom

ethi

um61

150

SmSa

mar

ium

62

(153

)Eu

Euro

pium

63

157

Gd

Gado

linium

64

159

TbTe

rbiu

m65

163

Dy

Dysp

rosiu

m66

165

Ho

Holm

ium67

167

ErEr

bium

68

169

TmTh

uliu

m69

173

Yb

Ytter

bium

70

175

LuLu

tetiu

m71

232

ThTh

orium

90

(231

)Pa

Prota

ctiniu

m91

238 U

Ura

nium

92

(237

)N

pNe

ptun

ium93

(242

)Pu

Plut

oniu

m94

(243

)A

mAm

erici

um95

(247

)C

mC

uriu

m96

(245

)B

kBe

rkeli

um97

(251

)C

fCa

liforn

ium98

(254

)Es

Eins

teiniu

m99

(253

)Fm

Ferm

ium

100

(256

)M

dM

ende

levium

101

(254

)N

oNo

beliu

m10

2

(257

)Lr

Lawr

enciu

m10

3

f Blo

ck

‣ La

ntha

noid

e

lem

ents

‣‣ A

ctin

oid

e

lem

ents

Ar

Sym

bol

Name Z

rela

tive

atom

icm

ass

atom

icnu

mbe

r

Key

© WJEC CBAC Ltd.