913925

3SUPERVISOR’S USE ONLY

9 1 3 9 2 M

© Mana Tohu Mātauranga o Aotearoa, 2017. Pūmau te mana. Kia kaua rawa he wāhi o tēnei tuhinga e tāruatia ki te kore te whakaaetanga tuatahi a te Mana Tohu Mātauranga o Aotearoa.

MĀ TE KAIMĀKA ANAKE

TAPEKE

Te Mātauranga Matū, Kaupae 3, 201791392M Te whakaatu māramatanga

ki ngā mātāpono taurite i ngā pūnaha waiwai

2.00 i te ahiahi Rāapa 15 Whiringa-ā-rangi 2017 Whiwhinga: Rima

Paetae Kaiaka KairangiTe whakaatu māramatanga ki ngā mātāpono taurite i ngā pūnaha waiwai.

Te whakaatu māramatanga hōhonu ki ngā mātāpono taurite i ngā pūnaha waiwai.

Te whakaatu māramatanga matawhānui ki ngā mātāpono taurite i ngā pūnaha waiwai.

Tirohia mēnā e rite ana te Tau Ākonga ā-Motu (NSN) kei runga i tō puka whakauru ki te tau kei runga i tēnei whārangi.

Me whakamātau koe i ngā tūmahi KATOA kei roto i tēnei pukapuka.

He taka pūmotu kua whakaritea ki te Puka Rauemi L3-CHEMMR.

Mēnā ka hiahia whārangi atu anō mō ō tuhinga, whakamahia ngā whārangi wātea kei muri o tēnei pukapuka, ka āta tohu ai i ngā tau tūmahi.

Tirohia mēnā e tika ana te raupapatanga o ngā whārangi 2 – 19 kei roto i tēnei pukapuka, ka mutu, kāore tētahi o aua whārangi i te takoto kau.

HOATU TE PUKAPUKA NEI KI TE KAIWHAKAHAERE HEI TE MUTUNGA O TE WHAKAMĀTAUTAU.

Te Mātauranga Matū 91392M, 2017

MĀ TE KAIMĀKA

ANAKE

TŪMAHI TUATAHI

(a) Kaputahemehangawaikawaitehauwaipūkōwhai,HF,metehauwaipūkane,HBr,inatāpirihiakitewai.

(i) Tuhiahewhāritetauhohengaoiawaikawakitewai.

Hauwaipūkōwhai,HF,kitewai:

Hauwaipūkane,HBr,kitewai:

(ii) Whakatauriteatekawengahikoongāmehanga0.150molL–1otewaikawapūkōwhai,HF,metewaikawapūkane,HBr.

Itōtuhinga,me:

• whakauruingāwhakaritengamōtētahimehangaheikawehiko

• tautohuingāmomokeirotoMEngākukūtangahāngai.

Kāorehetātaihangaehiahiatia.

2

QUESTION ONE

(a) Hydrogenfluoride,HF,andhydrogenbromide,HBr,bothformacidicsolutionswhenaddedtowater.

(i) Writeanequationforthereactionofeachacidwithwater.

Hydrogenfluoride,HF,withwater:

Hydrogenbromide,HBr,withwater:

(ii) Compareandcontrasttheelectricalconductivityof0.150molL–1solutionsofhydrofluoricacid,HF,andhydrobromicacid,HBr.

Inyouranswer,youshould:

• includetherequirementsforasolutiontoconductelectricity

• identifythespeciespresentANDtheirrelativeconcentrations.

Nocalculationsarenecessary.

3

Chemistry 91392, 2017

ASSESSOR’S USE ONLY

Te Mātauranga Matū 91392M, 2017

MĀ TE KAIMĀKA

ANAKE

(b) Itāpirihiahemehanga40.0mLote0.150molL–1HBrkite25.0mLotētahimehangahiriwapūkanetōpuni,AgBr.

(i) TuhiahewhāritemōtetauritengakeirotoitētahimehangatōpunioteAgBr.

(ii) WhakamāramahiangāhuringakaputakingākukūtangaongāmomokeitemehangatōpunioteAgBritetāpiritangaotemehangaHBr.

(iii) Tātaihiatekukūtangaongākatotehiriwa,Ag+,imuriitetāpiritangaotemehangaHBr.

Ks(AgBr)=5.00×10–13

MekīhetinoitinoatekukūtangaBr–keitemehangatōpunitaketakeoteAgBr.

4

(b) 40.0mLof0.150molL–1HBrsolutionwasaddedto25.0mLofasaturatedsilverbromide,AgBr,solution.

(i) WriteanequationfortheequilibriumoccurringinasaturatedsolutionofAgBr.

(ii) ExplainthechangesthatoccurtotheconcentrationsofthespeciesinthesaturatedsolutionofAgBrontheadditionoftheHBrsolution.

(iii) Calculatetheconcentrationofthesilverions,Ag+,aftertheHBrsolutionhasbeenadded.

Ks(AgBr)=5.00×10–13

AssumetheconcentrationofBr–intheoriginalsaturatedsolutionofAgBrisinsignificant.

5

Chemistry 91392, 2017

ASSESSOR’S USE ONLY

Te Mātauranga Matū 91392M, 2017

MĀ TE KAIMĀKA

ANAKE

TŪMAHI TUARUA

(a) Hepāpāhuangoikoretehaukini,NH3.

pKa(NH4+)=9.24 Ka(NH4

+)=5.75×10–10

(i) TātaitiatepHotētahimehanga0.105molL–1NH3.

(ii) Katāpirihiatewaikawapūhaumāotawaimeha,HCl,kitemehangaNH3kiataerāanōkite5:1teōwehengaoteNH3kiteNH4

+irotoitemehanga.

WhakatauhiatepHotēneimehanga,kaarotakeitekahakitepareitētahihuringaotepHinatāpirihiangārahingaitiotewaikawakaha,pāpāhuakaharānei

6

QUESTION TWO

(a) Ammonia,NH3,isaweakbase.

pKa(NH4+)=9.24 Ka(NH4

+)=5.75×10–10

(i) CalculatethepHofa0.105molL–1NH3solution.

(ii) Dilutehydrochloricacid,HCl,isaddedtotheNH3solutionuntiltheratioofNH3toNH4

+inthesolutionis5:1.

DeterminethepHofthissolution,andevaluateitsabilitytoresistachangeinpHwhensmallvolumesofstrongacidorbaseareadded.

7

Chemistry 91392, 2017

ASSESSOR’S USE ONLY

Te Mātauranga Matū 91392M, 2017

MĀ TE KAIMĀKA

ANAKE

(b) (i) Tuhiatewhāritemōtetauritengakeirotoitētahimehangatōpuniotekonukura(II)waihā,Cu(OH)2.

(ii) TuhiatekīangamōteKs(Cu(OH)2).

(iii) TātaihiatememehatangaoteCu(OH)2irōwaiite25°C.

Ks(Cu(OH)2)=4.80×10–20

(c) WhakamāramahiamaiheahaipikiaitememehatangaoteCu(OH)2inatāpirihiatewaikawapūhaumāotawaimeha.

8

(b) (i) Writetheequationfortheequilibriumoccurringinasaturatedsolutionofcopper(II)hydroxide,Cu(OH)2.

(ii) WritetheexpressionforKs(Cu(OH)2).

(iii) CalculatethesolubilityofCu(OH)2inwaterat25°C.

Ks(Cu(OH)2)=4.80×10–20

(c) ExplainwhythesolubilityofCu(OH)2increaseswhendilutehydrochloricacidisadded.

9

Chemistry 91392, 2017

ASSESSOR’S USE ONLY

Te Mātauranga Matū 91392M, 2017

MĀ TE KAIMĀKA

ANAKE

TŪMAHI TUATORU

Iwhakahaerehiahetātairangakukūmātetāpiriitemehangakonutaiwaihā0.112molL–1,NaOH(aq),kite20.0mLotemehangawaikawaewaro,CH3COOH(aq).

Kotewhāritemōtetauhohengako:

CH3COOH(aq) + NaOH(aq) → CH3COONa(aq) + H2O() Ka(CH3COOH)=1.74×10–5

Te ānau tātairanga kukū mō te CH3COOH ki te NaOH

00 5 10 15

Volume of NaOH added (mL)

pH

20 25 30 35 40 45 50 55

2

4

6

8

10

14

12

(a) Whakamahiatekōreromōteānautātairangakukūirungaake,katohukitetahaotetūtohuetinohāngaianaheitautohuitepaeōritenga.

Tūtohu pKa Tohua kia KOTAHI te pouaka i raro

Kōwhaimewaro 3.1

Poroporowaikawapūkane 6.3

Penopeirini(Phenolphthalein) 9.6

RōrahioteNaOHitāpiritia(mL)

10

QUESTION THREE

Atitrationwascarriedoutbyadding0.112molL–1sodiumhydroxidesolution,NaOH(aq),to20.0mLofethanoicacidsolution,CH3COOH(aq).

Theequationforthereactionis:

CH3COOH(aq) + NaOH(aq) → CH3COONa(aq) + H2O() Ka(CH3COOH)=1.74×10–5

Titration curve for CH3COOH versus NaOH

00 5 10 15

Volume of NaOH added (mL)

pH

20 25 30 35 40 45 50 55

2

4

6

8

10

14

12

(a) Withreferencetothetitrationcurveabove,putaticknexttotheindicatormostsuitedtoidentifytheequivalencepoint.

Indicator pKa Tick ONE box below

Methylyellow 3.1

Bromocresolpurple 6.3

Phenolphthalein 9.6

11

Chemistry 91392, 2017

ASSESSOR’S USE ONLY

Te Mātauranga Matū 91392M, 2017

MĀ TE KAIMĀKA

ANAKE

(b) (i) KotepHotemehangawaikawaewaro,CH3COOH(aq),he2.77imuaitetāpiritangaotētahiNaOH.

WhakaaturiamātetātaikotekukūtangaotemehangaCH3COOHhe0.166molL–1.

(ii) TātaihiatepHotemehangairotoitepuotoimuriitetāpiriite10.0mLote 0.112molL–1NaOHkite20.0mLotemehangawaikawaewaro,CH3COOH(aq).

Ka haere tonu te Tūmahi Tuatoru i te whārangi 14.

12

(b) (i) Theethanoicacidsolution,CH3COOH(aq),hasapHof2.77beforeanyNaOHisadded.

ShowbycalculationthattheconcentrationoftheCH3COOHsolutionis0.166molL–1.

(ii) CalculatethepHofthesolutionintheflaskafter10.0mLof0.112molL–1NaOHhasbeenaddedto20.0mLofethanoicacidsolution,CH3COOH(aq).

13

Chemistry 91392, 2017

ASSESSOR’S USE ONLY

Question Three continues on page 15.

Te Mātauranga Matū 91392M, 2017

MĀ TE KAIMĀKA

ANAKE

(c) KotepHitepaeōritengamōtetātairangakukūotewaikawaewarokitekonutai waihāhe8.79.

(i) Tautohuangāmomomatūkeirotoitepaeōritenga,ituaatuitewai.

(ii) Itētahitātairangakukūtuarua,katātaikukūtiahemehanga0.166molL–1otewaikawamewaro,HCOOH(aq),kitemehangaNaOH.KotepHitepaeōritengamōtēneihe8.28.

KotepHitepaeōritengamōtetātairangakukūCH3COOHhe8.79.

WhakatauriteangāuarapHitepaeōritengamōngātātairangakukūerua.

Ka(HCOOH)=1.82×10–4 Ka(CH3COOH)=1.74×10

–5

Kāorehetātaihangaehiahiatia.

14

(c) TheequivalencepointpHforthetitrationofethanoicacidwithsodiumhydroxideis8.79.

(i) Identifythechemicalspeciespresentattheequivalencepoint,otherthanwater.

(ii) Inasecondtitration,a0.166molL–1methanoicacidsolution,HCOOH(aq),istitratedwiththeNaOHsolution.TheequivalencepointpHforthistitrationis8.28.

TheequivalencepointpHfortheCH3COOHtitrationis8.79.

CompareandcontrastthepHvaluesattheequivalencepointforbothtitrations.

Ka(HCOOH)=1.82×10–4 Ka(CH3COOH)=1.74×10

–5

Nocalculationsarenecessary.

15

Chemistry 91392, 2017

ASSESSOR’S USE ONLY

Te Mātauranga Matū 91392M, 2017

MĀ TE KAIMĀKA

ANAKETAU TŪMAHI

He whārangi anō ki te hiahiatia.Tuhia te (ngā) tau tūmahi mēnā e tika ana.

16

17

Chemistry 91392, 2017

ASSESSOR’S USE ONLY

QUESTION NUMBER

Extra paper if required.Write the question number(s) if applicable.

Te Mātauranga Matū 91392M, 2017

MĀ TE KAIMĀKA

ANAKETAU TŪMAHI

He whārangi anō ki te hiahiatia.Tuhia te (ngā) tau tūmahi mēnā e tika ana.

18

19

Chemistry 91392, 2017

ASSESSOR’S USE ONLY

QUESTION NUMBER

Extra paper if required.Write the question number(s) if applicable.

91

39

2M

Level 3 Chemistry, 201791392 Demonstrate understanding

of equilibrium principles in aqueous systems

2.00 p.m. Wednesday 15 November 2017 Credits: Five

Achievement Achievement with Merit Achievement with ExcellenceDemonstrate understanding of equilibrium principles in aqueous systems.

Demonstrate in-depth understanding of equilibrium principles in aqueous systems.

Demonstrate comprehensive understanding of equilibrium principles in aqueous systems.

Check that the National Student Number (NSN) on your admission slip is the same as the number at the top of this page.

You should attempt ALL the questions in this booklet.

A periodic table is provided on the Resource Sheet L3–CHEMR.

If you need more room for any answer, use the extra space provided at the back of this booklet and clearly number the question.

Check that this booklet has pages 2 – 19 in the correct order and that none of these pages is blank.

YOU MUST HAND THIS BOOKLET TO THE SUPERVISOR AT THE END OF THE EXAMINATION.

English translation of the wording on the front cover