s14-1091-01 - revision science · pdf file2 (1091-01) examiner only section a answer all...
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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
2
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Examineronly
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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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
4
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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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6
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Examineronly
SECTION B
Answer all questions in the spaces provided.
8. (a) Hydrogenexistsasthreeisotopeswithrelativemassesof1,2and3.
Statethesimilaritiesanddifferencesinthecompositionofthesespecificisotopes. [2]
(b) Thefirsttwoelectronicenergylevelsinahydrogenatomareshownonthediagram.
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n = ∞
n = 2
n = 1
(i) Completethediagramtoshowenergylevelsn=3,n=4andn=5. [1]
(ii) Markwithanarrowtheenergychangecorrespondingtotheionisationenergyofhydrogen. [2]
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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.
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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.
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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
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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]
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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.
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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
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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]
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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]
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(1091-01)
16Examiner
only12. Hydromagnesiteisamixtureofmagnesiumcarbonateandsolubleimpurities.Astudentcrushed
somehydromagnesiteandaddedasampleofmass0.889gtoexcessdilutehydrochloricacidsothatthemagnesiumcarbonatecomponentreactedfully.
(a) Explainwhytherockwascrushedbeforebeingaddedtotheacid. [1]
(b) Writetheequationforthereactionbetweenmagnesiumcarbonateanddilutehydrochloricacid. [1]
(c) Thegas formedwascollected inagassyringeand its volumewasmeasuredoveraperiodoftime.Thevolumesandtimeswereplotted.Thevolumeof1molofgasundertheseconditionsis24.0dm3.
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00
100
50
200
150
5 10 15 20 25 30
Describewhathappenedtotherateofthereactionoverthe30minuteperiod. Explainwhyanychangesintherateoccurred. [3]
VolumeCO2/cm3
Time / minutes
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17
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(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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19
Examineronly
Questionnumber
Additional page, if required.Write the question number(s) in the left-hand margin.
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Questionnumber
Additional page, if required.Write the question number(s) in the left-hand margin.
Examineronly
(1091-01)
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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.