VCE Chemistry – Sample examination...CHEMISTRY (SAMPLE) 2 Version 2 – April 2017 SECTION A ot D...

S A M P L E

CHEMISTRYWritten examination

Day Date Reading time: *.** to *.** (15 minutes) Writing time: *.** to *.** (2 hours 30 minutes)

QUESTION AND ANSWER BOOK

Structure of bookSection Number of

questionsNumber of questions

to be answeredNumber of

marksA 30 30 30B 10 10 90

Total 120

• Studentsarepermittedtobringintotheexaminationroom:pens,pencils,highlighters,erasers, sharpeners,rulersandonescientificcalculator.

• StudentsareNOTpermittedtobringintotheexaminationroom:blanksheetsofpaperand/orcorrectionfluid/tape.

Materials supplied• Questionandanswerbookof41pages• Databook• Answersheetformultiple-choicequestionsInstructions• Writeyourstudent numberinthespaceprovidedaboveonthispage.• Checkthatyourname andstudent numberasprintedonyouranswersheetformultiple-choice

questionsarecorrect,andsignyournameinthespaceprovidedtoverifythis.• Unlessotherwiseindicated,thediagramsinthisbookarenotdrawntoscale.• AllwrittenresponsesmustbeinEnglish.At the end of the examination• Placetheanswersheetformultiple-choicequestionsinsidethefrontcoverofthisbook.• Youmaykeepthedatabook.

Students are NOT permitted to bring mobile phones and/or any other unauthorised electronic devices into the examination room.

©VICTORIANCURRICULUMANDASSESSMENTAUTHORITY2017

Version2–April2017

SUPERVISOR TO ATTACH PROCESSING LABEL HEREVictorian Certificate of Education Year

STUDENT NUMBER

Letter

CHEMISTRY(SAMPLE) 2 Version2–April2017

SECTION A – continued

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eaQuestion 1

MethaneisarenewableenergysourcewhenitisextractedfromA. naturalgas.B. coalseamgas.C. underthesedimentonoceanfloors.D. decomposingplantandanimalmaterial.

Question 2Whichstatementaboutpetrodieselandbiodieseliscorrect?A. Petrodieselemitssoot(smallcarbonparticles)whenburningisincomplete;biodieselispollutant-free.B. Petrodieselisproducedbydistillingcrudeoil;biodieselisproducedbyesterificationoffattyacids.C. Petrodieselconsistsoflong-chainhydrocarbons;biodieselcontainsbenzeneanditsderivatives.D. Petrodieselhasgreaterviscosityandhenceflowsmoreslowlyalongfuellinesthanbiodiesel.

Question 3Whichoneofthefollowingsubstancespresentinfoodprovidesthelowestamountofenergypergramforthehumanbody?A. tristearin(atriglyceride)B. alanine(anaminoacid)C. cellulose(apolysaccharide)D. fructose(amonosaccharide)

Question 4Asubstancethatcouldbeformedasaproductwhenapolysaccharideundergoesenzyme-catalysedhydrolysisisA. H2OB. CO2

C. C6H12O6

D. CH2OH.CHOH.CH2OH

SECTION A – Multiple-choice questions

Instructions for Section AAnswerall questionsinpencilontheanswersheetprovidedformultiple-choicequestions.Choosetheresponsethatiscorrect orthatbest answers thequestion.Acorrectanswerscores1;anincorrectanswerscores0.Markswillnotbedeductedforincorrectanswers.Nomarkswillbegivenifmorethanoneansweriscompletedforanyquestion.Unlessotherwiseindicated,thediagramsinthisbookarenotdrawntoscale.

Version2–April2017 3 CHEMISTRY(SAMPLE)

SECTION A – continuedTURN OVER

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Question 5Insulinisaproteinthatcontrolsaperson’sbloodsugarlevel.Astudenttestedfourseparatesamplesofpureinsulinintheformofsolidcrystals.Inwhichoneofthefollowingtestswouldtheprimarystructureofaninsulinsamplemostlikelybedisrupted?A. Dissolvethecrystalsinhydrochloricacid,addtheenzymepepsin,thenheatthesolution.B. Dissolvethecrystalsinwater,thenblendthesolutionataveryhighspeed.C. Dissolvethecrystalsinsodiumhydroxidesolution,thenheatthesolution.D. Dissolvethecrystalsinwater,thencoolthesolutioninanicebath.

Question 6Agroupofstudentsperformedacid-basetitrationstodeterminethemassofaspirininsometablets.Themanufacturerguaranteedthatthetrueaspirincontentwasbetween300mgand303mgpertablet.Whichsetofresultsforthemassofaspirininthetabletstestedwouldbedescribedasofrelativelyhighprecisionandrelativelylowaccuracy?A. 278mg,280mg,279mg,281mgB. 301mg,299mg,302mg,300mgC. 295mg,301mg,306mg,299mgD. 282mg,312mg,289mg,306mg

Question 7Whenhydrochloricacid,HCl,isaddedtoaluminiumsulfide,Al2S3,thehighlytoxicgashydrogensulfide,H2S,isevolved.Theequationforthisreactionis

Al2S3(s)+6HCl(aq)→2A1C13(aq)+3H2S(g)

Ifexcesshydrochloricacidisaddedto0.200molofaluminiumsulfide,thenthevolumeofhydrogensulfideproducedatstandardlaboratoryconditions(SLC)willbeA. 1.63LB. 4.90LC. 7.35LD. 14.7L



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Use the following information to answer Questions 8 and 9.GhimLiwishestoinvestigatetheeffectofpHontheactivityoftheenzymeprotease.

Question 8GhimLiperformshertestsinflasksthatareplacedinawaterbathtokeeptheflasksandtheircontentsataconstanttemperatureof37°C.Undertheseconditions,thetemperatureatwhichtheexperimentisconductedisreferredtoastheA. control.B. dependentvariable.C. controlledvariable.D. independentvariable.

Question 9Inonetest,GhimLiraisesthepHofasolutioncontainingthereactantsandtheenzymeto13.0Whichoneofthefollowingwilloccur?A. Therateofthereactionthattheenzymeiscatalysingwillincrease.B. Thehydrogenbondingholdingtheenzymeinitsshapewillnotbedisrupted.C. AnyNH3

+andCOOHgroupsontheenzymewillbechangedtoNH2andCOO–groups.D. Thenatureofthebondinginteractionsbetweentheenzymeandthesubstratewillremainthesame.



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Question 10Beta-caroteneisfoundnaturallyinorangeandyellowvegetables.Inhumans,itcanbeconvertedtovitaminA1, asshownintheflowchartbelow.

O

OH

beta-carotene

retinal

retinol(vitamin A1)

TheinformationintheflowchartindicatesthatA. allthreecompoundscanbedistinguishedbytheirinfra-redspectra.B. allthreecompoundsareclassifiedassaturatedhydrocarbons.C. allthreecompoundswouldbehighlysolubleinwater.D. retinalisaketone,whileretinolisanalcohol.



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Question 11Themassspectrumofpropanoicacid,CH3CH2COOH,isshownbelow.

10 15 20 25 30 35 40 45m/z

50 55 60 65 70 75

100

80

60

40

relativeintensity

20

0

Data:SDBSWeb;http://sdbs.db.aist.go.jp, NationalInstituteofAdvancedIndustrialScienceandTechnology

Thepeakatm/z74A. representstheparentioncontainingthecarbon-13isotope.B. representsthespecies[CH3CH2COOH]+.C. representsthespeciesCH3CH2COOH.D. iscommonlyknownasthebasepeak.

Question 12Considerthefollowingenergyprofileforaparticularchemicalreaction,whereI,IIandIIIrepresententhalpychangesduringthereaction.

I

II

IIIenthalpy(kJ mol–1) reactants

products

Whichoneofthefollowingstatementsiscorrect?A. Theactivationenergyforthereversereactionis(III–II).B. ThenetenergyreleasedfortheforwardreactionisrepresentedbyII.C. TheenergyrequiredtobreakthereactantbondsisrepresentedbyII.D. TheenergyreleasedbytheformationofnewbondsisrepresentedbyI.



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Question 13Theoxidationofsulfurdioxideisanexothermicreaction,asshownintheequationbelow.Thereactioniscatalysedbyvanadium(V)oxide.

2SO2(g)+O2(g)→2SO3(g)

Whichoneofthefollowingenergyprofilediagramscorrectlyrepresentsboththecatalysedandtheuncatalysedreactions?

enthalpy(kJ mol–1)




A. B.

C. D.

catalysed reactionuncatalysed reaction

Key

Question 14Theequationforthefermentationofglucose,C6H12O6,inthepresenceofyeastisshownbelow.

C6H12O6(aq)yeast

2C2H5OH(aq)+2CO2(g)

Data

Reactant or product Concentration (g mol–1)

C6H12O6 180.0

C2H5OH 46.0

CO2 44.0

Whatisthepercentageatomeconomyfortheproductionofethanolbythisreaction?A. 25.6%B. 50.0%C. 51.1%D. 100%



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Use the following information to answer Questions 15 and 16.Thenumberofmoleculespresentinasampleofoxygen,O2,gasincertainconditionshasadistributionofkineticenergiesshownbyCurve1inthegraphbelow.Afteronechangeismadetotheoriginalconditions,asecondcurveisdrawnonthesameaxes(Curve2).Theareasunderthetwocurvesarethesame.

Curve 1

Curve 2number of

O2 molecules

kinetic energy (J) Ea

Question 15WhatchangewasmadetotheoriginalconditionsshownbyCurve1,whichledtothedistributionshownbyCurve2?A. TheO2samplewasheated.B. MoreO2moleculeswereaddedtothecontainer.C. Apowderedcatalystwasblownintothecontainer.D. SomeO2moleculeswereremovedfromthecontainer.

Question 16Onthegraph,EarepresentstheactivationenergyforareactionbetweenO2andanothergas.Underitsfinalconditions,representedbyCurve2,thenumberofmoleculesofO2inthesamplethathavesufficientenergytoreactisrepresentedbytheA. areaunderCurve2totherightofEa.B. maximumheightofCurve2.C. totalareaunderCurve2.D. heightofCurve2atEa.



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Question 17Largedepositsofmethanehydratehavebeendiscovereddeepunderthesedimentontheoceanfloor.Ithasbeensuggestedthatmethanehydratedepositscouldbecommerciallyminedtoprovideacleanfueloncethetrappedmethaneisextracted.Methanehydratehasacomplexstructure.ThesimplifiedformulaformethanehydrateisCH4·6H2O.Theamountofenergyreleasedbythecompletecombustionofmethaneextractedfroma1.00kgsampleofCH4·6H2OatSLCisA. 8.89×102kJB. 7.17×103kJC. 4.30×104kJD. 5.56×104kJ

Question 18InrechargeablebatteriesA. theanodealwayshasanegativepolarity.B. whenthecelldischarges,itactsasagalvaniccell.C. whenthecellrecharges,electronsmustflowintothepositiveelectrode.D. theproductsofthehalf-cellreactionsmigratebackandforthbetweentheelectrodes.

Question 19

H HC

H

CH C C C H

H HH H

H

H

H

HHH

C

C HH

C

H

HH

C

WhatisthecorrectIUPACsystematicnameforthecompoundshownabove?A. 4,5-dimethylheptaneB. 3,4-dimethylheptaneC. 4-methyl-5-ethylhexaneD. 2-ethyl-3-methylhexane

Question 20CoenzymeQ10isasubstanceproducedbythehumanbody.Itisinvolvedintheprocessofcellularrespiration,whichistheprimarysourceofenergyinbodycells.InwhichoneofthefollowingprocessesiscoenzymeQ10mostlikelyinvolved?A. favouringtheforwardreactionofcellularrespirationB. actingasanantioxidanttoremoveelectronsfromthecellC. enablingthetransportofcarbondioxideawayfromthecellD. changingtheorientationofatomsattheactivesiteofthesubstrate



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Use the following information to answer Questions 21–23.Potassiummetal,K,wasdiscoveredin1807inEnglandbySirHumphryDavy.Small,shinybeadsofmoltenpotassiumwereproducedwhenanelectriccurrentfromanearlybatterywaspassedthroughmoltenpotassiumhydroxide,KOH.Theelectrolyticcellisshowninthediagrambelow.

anode(graphite)

cathode(graphite)

globules ofmolten potassium

molten KOH

strong heat

Question 21Whatcurrentwasflowingthroughthecellif0.152gofmoltenpotassiumwasproducedinthefirstminute?A. 4.00×10–8 AB. 2.42×10–6 AC. 6.25AD. 375A

Question 22 IfinsteadDavyhadelectrolyseda1.0MKOHsolutionat25°C,stillusinggraphiteelectrodes,whatmainproductswouldbeobservedattheanodeandcathode,respectively?A. carbondioxidegas,hydrogengasB. oxygengas,moltenpotassiumC. carbondioxidegas,oxygengasD. oxygengas,hydrogengas

Question 23Today,somemetalsarestillextractedfromtheirmoltencompoundsusingelectrolyticcells.Aluminiumisextractedfromitsmoltenoxide,Al2O3,byelectrolysis.If0.60molofelectronsarepassedthroughmoltenAl2O3,whatamountofaluminiumwillbeproduced?A. 0.20molB. 0.30molC. 0.60molD. 0.90mol



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Use the following information to answer Questions 24 and 25.Titaniumisawidelyusedmetalthatisextractedfromitsore,titaniumdioxide,TiO2,intwostages.

Stage1 Theimpureoxideisconvertedtotitanium(IV)chloride,TiCl4,at1000°C. Theequationforthisreactionis

Reaction1 TiO2(s)+2Cl2(g)+2C(s)→TiCl4(g)+2CO(g)

TheTiCl4isthenpurifiedinanatmosphereofargongas.

Stage2 ThepureTiCl4vapourisreactedwithmoltenmagnesium,Mg,inanatmosphereofargongasat1000°C. Theequationforthisreactionis

Reaction2 TiCl4(g)+2Mg(l)→Ti(s)+2MgCl2(l)

Thisreactiontakesabouttwodays.Thetitaniummetalproducedisthenprocessedtopurifyit.

Question 24Whichstatementaboutthetworeactionsiscorrect?A. TheconjugateoxidisingagentofTiCl4inReaction2isTi.B. TheconjugatereducingagentofCinReaction1isCO.C. Boththecarbonandmagnesiumactasreducingagents.D. InReaction1,chlorinegasoxidisesTiO2toTiCl4.

Question 25Inthetworeactions,themostlikelyroleofargongasistoA. reducetheriskofanexplosionoccurringathightemperatures.B. drivethereactionsforwardtoincreasethepercentageyield.C. excludeoxygenandhencepreventTifromformingoxides.D. actasacatalysttolowerthecostofproduction.

Question 26Hydrogen,H2,isproducedonanindustrialscalefrommethane,CH4.Theequationforthereactionis

2H2O(g)+CH4(g)⇌CO2(g)+4H2(g)

Ifaninertgasisaddedtotheequilibriumsystemataconstanttemperatureandaconstantvolume,theconcentrationofH2willA. increase.B. decrease.C. notchange.D. decreasethenincrease.



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Question 27Whichoneofthefollowingskeletalstructuresrepresentsaprimaryamide?

H

H

H

HN

N

O

O

O

HN

O

H

H

HH

H

HCN

N

H

HH

O

O

A. B.

C. D.

Question 28

NaOH(aq)

CH3CH2CH2CH2OH

HCl, solid AlCl3 catalyst NH3 (dissolved in ethanol)X Y Z

Whatarethesemi-structuralformulasofX,YandZforthereactionpathwayshownabove?

X Y Z

A. CH3CH2CH2CH3 CH3CH2CH2CH2Cl CH3CH2CH2CH2NH2

B. CH3CH2CHCH2 CH3CH2CHClCH3 CH3CH2CHNH2CH3

C. CH3CH2CH2CH3 CH3CH2CH2CHCl2 CH3CH2CH2CONH2

D. CH3CH2CHCH2 CH3CH2CH2CH2Cl CH3CH2CH2CH2NH2


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END OF SECTION ATURN OVER

Use the following information to answer Questions 29 and 30.Rubystandardisedacitricacid,C6H8O7,solutionagainstapreviouslystandardisedsodiumhydroxide,NaOH,solution.Theequationforthetitrationreactionwas

C6H8O7(aq)+3NaOH(aq)→Na3C6H5O7(aq)+3H2O(l)

Question 29Ruby’sresultsareshowninthetablebelow.

Quantity Measurement

volumeofNaOHsolution 20.00mL

molarityofNaOHsolution 0.125M

meantitreofC6H8O7solution 23.6mL

Whatwastheconcentrationofcitricacidinthesolution?A. 0.035MB. 0.049MC. 0.105MD. 0.316M

Question 30UnknowntoRuby,theNaOHsolutionsuppliedhadabsorbedsomecarbondioxide,CO2,fromtheair.CO2isweaklyacidicandreactswithNaOH.WhattypeoferrorwillthiscontaminationoftheNaOHleadtointhisanalysis,andwhatwillbeitslikelyeffectonthemeantitreofcitricacid?

Type of error Likely effect on the mean titre of citric acid

A. random greaterthanwouldbeifnocontaminationhadoccurred

B. random lowerthanwouldbeifnocontaminationhadoccurred

C. systematic greaterthanwouldbeifnocontaminationhadoccurred

D. systematic lowerthanwouldbeifnocontaminationhadoccurred


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SECTION B – Question 1–continued

Question 1 (7marks)Whenmakingsaladsandwiches,Tomprefershomemademayonnaiseonhisbread,whileGitaprefersasoft,solidspreadthatismadefromhydrogenatedvegetableoil.Tommakeshismayonnaisewitholiveoil.Whenoliveoilismetabolised,onefattyacidthatisproducedislinoleicacid.Itsskeletalstructureisshownbelow.

O

OH

linoleic acid

Gita’sfavouritevegetableoilspreadismanufacturedfromcanolaoil.Whencanolaoilismetabolised,onefattyacidthatisproducediselaidicacid.Itsskeletalstructureisshownbelow.

O

OH

elaidic acid

a. Onbothoftheskeletalstructuresabove,circleallC=Cdoublebondsthatshowacisconfiguration. 1mark

b. Islinoleicacidclassifiedasanomega-3fattyacidorasanomega-6fattyacid?Justifyyouranswer. 2marks

SECTION B

Instructions for Section BAnswerallquestionsinthespacesprovided.Writeusingblueorblackpen.Givesimplifiedanswerstoallnumericalquestions,withanappropriatenumberofsignificantfigures;unsimplifiedanswerswillnotbegivenfullmarks.Showallworkinginyouranswerstonumericalquestions;nomarkswillbegivenforanincorrectanswerunlessitisaccompaniedbydetailsoftheworking.Ensurechemicalequationsarebalancedandthattheformulasforindividualsubstancesincludeanindicationofstate,forexample,H2(g),NaCl(s).Unlessotherwiseindicated,thediagramsinthisbookarenotdrawntoscale.


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SECTION B – continuedTURN OVER

c. Chooseoneofthefattyacidsbelowbyticking()theboxbesideitandindicateifitissaturated,monounsaturatedorpolyunsaturated. 1mark

linoleicacid

elaidicacid

d. Consideratriglyceridethatcontainsthreelinoleicacidtailsandatriglyceridethathasthreeelaidicacidtails.

Predictwhichofthesetwotriglycerideswouldhavethehighermeltingpoint.Justifyyouranswer. 3marks


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SECTION B – continued

Question 2 (5marks)Amylaseisanenzymethatcatalysesthehydrolysisofstarchandsugarsintoglucose.Therearetwomodelsthatexplainhowenzymeswork:thelock-and-keymodelandtheinducedfitmodel.

a. Applyyourunderstandingofthelock-and-keymodeltodrawandannotateasetofsimplediagramstoexplainhowamylasecatalysesthehydrolysisofadisaccharide. 3marks

b. Ifinsteadtheamylasecatalysesthehydrolysisofadisaccharideaccordingtotheinducedfitmodel,inwhatway(s)wouldtheinteractionbedifferent?Youmayuselabelleddiagramstoexplainyouranswer. 2marks


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Question 3 (6marks)Thefollowingtablelistsastudent’ssummarynotesaboutfoodchemistry.Itcontainssomecorrectandincorrectstatements.

Statementnumber

Statement

1 Themonomersofstarcharebondedbyglycosidiclinksandthemonomersofproteinsarebondedbypeptidelinks.

2 Thehydrolysisofaproteinrequiresthepresenceofbothanenzymeandacoenzyme.

3 Anenzymecanonlycatalyseaspecificbiochemicalreactiononce,sinceitisconsumedinthereaction.

4 Sucroseisadisaccharideformedbyacondensationreactionbetweenthemonomersglucoseandfructose.

5 Fatshavelowermeltingpointsthanoilsbuttheyarebothclassifiedastriglycerides.

6 Whenanoilishydrolysed,glycerolandthreefattyacidsareproduced.

7 Oxidativerancidityoccurswhenasaturatedtriglycerideisexposedtooxygen.Thiscausesthesaturatedtriglyceridetoformcompoundssuchasaldehydesandketones.

8 Antioxidantsarereducingagentsthatslowdowntherateofoxidativerancidity.

9 Thedenaturationofaproteinisthebreakingdownofitssecondaryandtertiarystructures.

10 Zwitterionsareionsthatareproducedwhenaproteinisbrokendownbyheat.

a. Identifytwocorrectstatementsbywritingthestatementnumbersintheboxesprovidedbelow. 2marks

Statementnumber Statementnumber

b. Identifytwoincorrectstatementsbywritingthestatementnumbersinthetableprovidedbelow. Explainwhyeachstatementisincorrect. 4marks

Statement number

Explanation


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Question 4 (6marks)Claireisanalysingasampleofpainttodeterminetheorganicsolventsthatarepresent.Sheseparatesthedifferentcompoundsandanalyseseachoneusinginfra-red(IR)spectroscopy,and13Cand1HNMRspectroscopy.ClairefindsthatoneofthecompoundsthatsheisolateshasamolecularformulaofC5H10O.Theresultsforthiscompoundforeachtypeofspectroscopyusedareshowninthespectraonpages18–20.Usetheinformationprovidedtoanswerthequestionsonpage21.

wave number (cm–1)

IR spectrum100

50

0

transmittance(%)

4000 3000 2000 1500 1000 500



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SECTION B – Question 4–continuedTURN OVER

200220 180 160 140 120 100 80ppm

60 40 20 0

13C NMR spectrum



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9 8 7 6 5ppm

4 3 2 1 0

1H NMR spectrum


1H NMR data

Chemical shift Splitting pattern

1.0 3

2.4 4


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a. FromtheIRspectrumofthecompound,identifytheorganicfamilytowhichthiscompoundbelongs.Justifyyouranswerbyreferringtotherelevantwavenumber. 2marks

b. Drawastructuralformulaforthiscompoundthatisconsistentwiththedataprovided.Explainyourreasoningbyreferringtothisdata. 4marks


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Question 5 (12marks)Ascorbicacid,alsocalledvitaminC,isanorganicacidthatplaysavitalroleinhumanhealth.ItsmolecularformulaisC6H8O6.CitrusfruitareacommonsourceofvitaminC.Inthefollowingexperiment,theconcentrationofvitaminCpresentinthejuicefromabatchoffreshlysqueezedlemonswasdeterminedbycarryingoutadirectredoxtitrationagainstthetri-iodideion.Thetri-iodideionisproducedwheniodinesolution,I2,andiodidesolution,I–,aremixedtogether.

I2(aq)+I–(aq)→ I3–(aq)

Theoverallredoxreactionoccurringis

C6H8O6(aq)+I3–(aq)→C6H6O6(aq)+2H+(aq)+3I–(aq)

a. Identifytheoxidisingagentinthistitrationreaction. 1mark


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Forthetitration,a20.00mLsampleofpurelemonjuicewasmadeupto250.00mLwithde-ionisedwaterina250mLvolumetricflask.Then,25.00mLaliquotsofthedilutedlemonjuiceweretransferredtoconicalflasksandtitratedagainstapreviouslystandardised2.000×10–4MI3–solution,whichwaslightbrownincolour.Todetectthe endpoint,starchwasaddedwhenthemixturebecameaverypalebrown.Thisstarchindicatorturnedfromdeepbluetocolourlessattheendpoint.Theaveragetitrewasfoundtobe15.65mL.

b. i. Calculatetheamount,inmoles,ofI3–presentintheaveragetitre. 1mark

ii. Calculatetheamount,inmoles,ofC6H8O6presentineach25.00mLaliquotofdilutedlemonjuice. 1mark

iii. CalculatethemolarityofC6H8O6intheoriginalsampleofpurelemonjuice.Hence,statetheconcentrationofvitaminCinthelemonjuice. 3marks


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c. TheskeletalstructuresofvitaminCandvitaminD3areshownbelow.

O O

OO

O

O

H

H

H

H

vitamin C

OH

vitamin D3

i. Aswithmostorganiccompoundsmetabolisedbythehumanbody,vitaminsexistaspairsofopticalisomers.OnlytheopticalisomerofvitaminC,whichisshownintheskeletalstructureabove,occursnaturally.

OntheskeletalstructureofvitaminC,circlethetwochiralcarbons. 2marks

ii. Inhumans,theenzymeknownasL-ascorbateoxidasecanbreakdownonlythenaturallyoccurringopticalisomerofvitaminC.

Explainwhythisenzymewouldnotbreakdowntheotheropticalisomer. 2marks

iii. Theanalysisofthelemonjuiceinpart b.waspossiblebecausevitaminCiswater-soluble.

Intermsofitsstructure,explainwhyvitaminCiswater-solublewhilevitaminD3isnot. 2marks


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Question 6 (6marks)Theglycaemicindex(GI)isavalueassignedtofoodsbasedonhowslowlyorquicklythecarbohydratesinfoodsarebrokendowntocauseanincreaseinbloodsugarlevels.TheGIofpureglucoseisassignedavalueof100.Foodsmaybeclassifiedashavingalow,mediumorhighGIaccordingtothevaluesgiveninthetablebelow.

Glycaemic index (GI) Value

low ≤55

medium 56–69

high ≥70

CarbohydrateswithlowGIvaluesaremoreslowlydigested,absorbedandmetabolised,andcausealowerandslowerriseinbloodglucoselevelsthancarbohydrateswithhigherGIvalues.In2016,aresearchteamatTuftsUniversityundertookastudytodeterminewhetherGIvaluesareaccurateandreproducible.Sixty-threevolunteerswererecruitedforthestudythatinvolvedsixtestingsessionsover12weeks.Eachsessioninvolvedthevolunteersrandomlybeinggivenafoodsampleofwhitebread (asimplecarbohydratethatwasusedasthetestfood)oraglucosedrink(usedasareferencecontrol).Eachfoodsamplecontained50gramsofavailablecarbohydrate.BloodglucoselevelsweremeasuredatmultiplepointsforfivehoursaftereatingandtheGIvaluewascalculatedusingstandardformulas.TheteamfoundthatthemeanGIvalueofwhitebreadforthestudypopulationwas62,placingitinthecategoryoffoodswithamediumGIvalue.However,deviationsaveraged15pointsineitherdirection,effectivelyplacingwhitebreadinallthreeGIcategories.TheteamfoundthatvariationsinGIvaluesdifferedacrossindividualsaswellaswithinthesameindividualbetweentrials,butbiologicalfactorssuchasgender,bodymassindexandphysicalactivityhadonlyaminoreffectonthevariabilityofGIvalues.

a. WhyisglucoseusedasthestandardfordeterminingGIvalues? 1mark

b. Whatismeantbytheterm‘availablecarbohydrate’? 1mark


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c. Glucoseisusedasthemainfuelbythebrainandnervoussystem,andisthepreferredsourceoffuelformostorgansandmusclesduringexercise.

SuggestwhyathletesmayprefertoincludefoodswithhighGIvaluesintheirdiet. 2marks

d. Withreferencetothefindingsofthestudy,commentonafoodlabelclaimthataproducthasalowGIvalue. 2marks


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Question 7 (10marks)Acarmanufacturerisplanningtosellhybridcarspoweredbyatypeofhydrogenfuelcellconnectedtoanickelmetalhydride,NiMH,battery.Arepresentationofthehydrogenfuelcellisshownbelow.

NiMHbattery

H2(g) O2(g)

product outH2(g) → 2H+(aq) + 2e–

A

anode

B

cathodeswitch

polymerelectrolytemembrane

C

Theoverallcellreactionis

2H2(g)+O2(g)→2H2O(g)

a. i. Onthediagramabove,indicatethepolarityoftheanodeandthecathodeincirclesAandB,andidentifytheproductofthereactioninboxC. 2marks

ii. Writeanequationforthereactionthatoccursatthecathodewhentheswitchisclosed. 1mark

Cathodereaction

iii. Giveoneadvantageofusingahydrogenfuelcelltosupplyenergyratherthanusingpetrol, whichismadefromcrudeoil. 1mark


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b. ThestoragebatterytobeusedinthehybridcarscomprisesaseriesofNiMHcells.MHrepresents ametalhydridealloythatisusedasoneelectrode.Theotherelectrodecontainsnickeloxidehydroxide,NiOOH.TheelectrolyteisaqueousKOH.

electric carmotor

+

–

KOH(aq)

direction of electron flow

Thesimplifiedequationforthereactionattheanodewhilerechargingis

Ni(OH)2(s)+OH–(aq)→NiOOH(s)+H2O(l)+e–

Thesimplifiedequationforthereactionatthecathodewhilerechargingis

M(s)+H2O(l)+e– →MH(s)+OH–(aq)

i. Whatistheoverallequationforthedischargingreaction? 1mark

ii. Intheboxesonthediagramabove,indicatewhichistheMHelectrodeandwhichistheNiOOHelectrode. 1mark

iii. Intheboldboxprovidedabovethecelldiagram,useanarrow,→or←,toindicatethedirectionoftheelectronflowasthecellisdischarging. 1mark

iv. Thebatterydischargedfor60minutes,producingacurrentof1.15A.

Whatmass,ingrams,ofNiOOH,wouldbeusedduringthisperiod? 3marks


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Question 8 (10marks)Carbonmonoxide,CO,reactswithammonia,NH3,toproducehighlytoxichydrogencyanide,HCN,aswellascarbondioxide,CO2,andhydrogen,H2.Thisreactionisendothermicandtheequationforthisreactionisshownbelow.

2CO(g)+NH3(g)⇌HCN(g)+CO2(g)+H2(g)

a. i. Writetheexpressionfortheequilibriumconstantforthisreaction. 1mark

ii. Inoneexperiment,amixtureofCOandNH3,togetherwithasuitablecatalyst,wasinjectedintoasealed100mLgassyringeandallowedtocometoequilibrium.

Whentheequilibriummixturewasanalysedataparticulartemperature,thefollowingconcentrationsweredetermined.

[CO]=0.0025M [NH3]=0.00125M [HCN]=0.0042M

Calculatetheequilibriumconstantforthereactionatthistemperature. 2marks

b. AnalyststheninvestigatedtheeffectoftwodifferentchangesontheequilibriumsystembymonitoringtheamountofHCN(inmoles)presentinthegasmixtureoveraperiodoftime.

i. Tick()theappropriateboxinthetablebelowtoshowtheexpectedeffectontheamountofHCN (inmoles)presentinthegasmixtureasaresultofeachchange. 2marks

Change investigated Expected effect on the amount of HCN

Increase Decrease No effect

Halvethevolumeofthegasmixture,keepingthetemperatureconstant.

Returnthevolumeofthegasmixtureto 100mL,theninjectsomepowderedpalladiumintothegassyringe.(PalladiumabsorbsH2gasontoitssurface.)


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ii. Completetheconcentration–timegraphontheaxesprovidedbelow,toshowwhatwillhappento theconcentrationsofHCNandNH3inanequilibriummixturewhenthevolumeofthegas mixtureissuddenlyhalvedataconstanttemperature. 2marks

Concentration–time graph for the equilibrium system

0

0.001

0.002

0.003

0.004

0.005

0.006concentration

(mol L–1)

0.007

0.008

0.009

0.010

time (s)

KeyHCNNH3

volume halvedat this point


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c. COgasisproducedwhenahydrocarbonfuel,suchasbutane,C4H10,isburntinalimitedairsupply.

WritethebalancedequationforthecombustionofC4H10inalimitedairsupply,assumingthatCOistheonlycarbon-basedoxidationproduct. 1mark

d. COpoisoningisonedangerfacedbyrescuersenteringaburningbuilding,soitisessentialthatrescuerswearappropriatebreathingapparatus.

HaemoglobininredbloodcellstakesupO2fromtheairinanequilibriumreactionrepresentedbyEquation1.

Equation1 Hb4(aq) + 4O2(aq) ⇌ Hb4O8(aq) K1

haemoglobin haemoglobin-oxygen complex

COmoleculescanalsoattachtohaemoglobinmolecules.TheequilibriumreactioninvolvedisrepresentedbyEquation2.

Equation2 Hb4(aq) + 4CO(aq) ⇌ Hb4(CO)4(aq) K2

haemoglobin haemoglobin-carbonmonoxide complex

IftheconcentrationofCOintheairinsideaburningbuildingincreasesto800ppm,anyonewhoisexposedtothiswillquicklyloseconsciousness,evenifoxygenispresent.Torevivethem,theymustbegivenpureoxygen.

WhatconclusionscanbemadeabouttherelativevaluesofequilibriumconstantsK1andK2? 2marks


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Question 9 (14marks)Agroupofstudentswassetthetaskofinvestigatingthemolarheatofcombustionofglucoseusingprimaryandsecondarydatathatwasobtainedfromtwodifferentexperimentaltechniques.Thefirstexperimentaltechniqueusedtofindthemolarheatofcombustionofglucoseinvolvedcollectingprimarydata.Thestudentssetuptheapparatusasshownbelow.Theyweighedoutasampleofpureglucosepowderintothecrucible,readyforthecombustion.Theyalsoweighedout150.0gofwaterintothecoppercalorimeterpotandmeasuredtheinitialtemperatureofthewater.

Experimental technique 1

stirrer

copper calorimeter pot

water

crucible

pipeclay triangle

tripodglucosepowder

thermometer

clamp

retortstand

heat-proof mat

Beforeburningtheglucosetodetermineanexperimentalvalueofitsheatcontent,thestudentsdecidedtocalculatethepredictedmaximumtemperatureriseofthewater.ThesetofdatatheyusedisshowninTable1.

Table 1. Data for determining the predicted maximum temperature rise of the water


massofglucosepowder 2.002g

massofwater 150.0g

specificheatcapacityofwater 4.182Jg–1°C–1

initialtemperatureofwater 21.3°C

publishedmolarheatofcombustionofglucose 2805kJmol–1

molarmassofglucose 180.0gmol–1


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a. i. UsethedatafromTable1tocalculatethepredictedmaximumtemperatureriseofthewater. 3marks

ii. Thestudentsthensafelyignitedtheglucosepowder.Whenthepowderstoppedburning,thestudentsrecordedtheactualtemperatureriseofthewater.Theydeterminedthatthefinaltemperatureofthewaterwas48.5°C.

Comparetheexperimentaltemperaturerisewiththevaluethatthestudentspredictedandhencecommentontheaccuracyofthevalueoftheheatofcombustionofglucosethatthestudentswouldhaveobtainedusingthisexperimentaltechnique. 2marks


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Thesecondexperimentaltechniqueforfindingthemolarheatofcombustionofglucoseinvolvedusingatypicalcommercialbombcalorimeter.Theapparatussetupbythestudentsisshownbelow.

Experimental technique 2

thermometer

insulatedcontainer

sealed vessel glucose powder

stirrer

ignition wire

water

pure oxygen in excess

Thestudentswereabletoobtainthefollowingsecondarydatafromacommercialfoodanalysislaboratory.

Table 2. Electrical calibration of bomb calorimeter


current 1.78A

potentialdifference 5.65V

timecurrentpassed 135s

temperatureriseofwater 1.150°C

Table 3. Combustion of glucose


massofglucose 1.324g

temperatureriseofwater 17.32°C


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b. i. Showbycalculationthatthecalibrationfactorofthebombcalorimeterobtainedbythestudentsis1180J°C–1. 2marks

ii. Using1180J°C–1asthecalibrationfactorofthebombcalorimeter,calculatethemolarheatofcombustionofglucoseinJmol–1. 3marks

iii. Comparetheexperimentalvaluefrompart b.ii.withthepublishedvalueofthemolarheatofcombustionofglucosegiveninTable1. 1mark

c. i. IdentifyoneofthedesignfaultsofExperimentaltechnique1thatwouldhavecontributedtoitslessaccurateresults. 1mark

ii. ExplainhowthedesignfeaturesofExperimentaltechnique2overcamethedesignfaultidentifiedinpart c.i.toobtainmoreaccurateresults. 2marks


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Question 10 (14marks)ForhisextendedVCEChemistryexperimentalinvestigationproject,Chrisdecidedtoinvestigatewhetherthereisarelationshipbetweentherateofthereactionbetweenmagnesium,Mg,andhydrochloricacid,HCl,andtheconcentrationoftheacid.ThefollowingisanextractfromthescientificposterthatChrisproduced.

Question under investigation:Istherearelationshipbetweentherateofthereactionbetweenmagnesium,Mg,anddifferentconcentrationsofhydrochloricacid,HCl?

Equation for the reaction: Mg(s)+2H+(aq)→Mg2+(aq)+H2(g)

Experimental design:FourdifferentconcentrationsofHClweretested.Therateofeachreactionwasinvestigatedbymeasuringthevolumeofhydrogen,H2,gasproducedat60-secondintervals.

Hypothesis: Thegreatertheconcentrationoftheacid,thefasterthereactionwillbe.Iexpectthisbecause,forareactiontooccur,H+ionsmustcollidewithMgatoms.Thegreatertheconcentrationoftheacid,themorefrequentlytheH+ionswillcollidewiththesurfaceoftheMgandsothegreatertheamountofH2gasthatwillbeproduced.

a. Inhishypothesis,doesChrisdemonstrateanunderstandingofthechemistrythatisrelevanttothisexperimentalinvestigation?Explainyourreasoning. 2marks

Inhisposter,Chrisoutlinedhowtheexperimentalinvestigationwasconducted.Anextractfromhismethodologyisshowninthetablebelow.

Methodology: First,thevariableswereidentified.ThedecisionsImadeareshowninTable1.

Table 1. The variables identified

Variable Classification Details

massofMg controlledvariable ThefirstpieceofMgribbonwasweighedandmeasured,thenthesamelengthofMgwasusedforeachconcentrationofHCltested.

concentrationofHCl dependentvariable 0.5M,1.0M,1.5Mand2.0MsolutionsofHClweretested.

volumeofHCl controlledvariable 50.0mLwasusedforeachtest,measuredusingagraduatedmeasuringcylinder.


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b. IsChris’sidentificationoftheconcentrationofHClasthedependentvariablecorrect?Giveareasonforyouranswer. 1mark

Chris’sposterincludedadiagramoftheexperimentalset-up,supportedbyshortnotes,asshownbelow.

The experimental set-up:

syringe for injecting HCl

H2 gas collectingin graduatedmeasuring cylinder

stopwatch tabletdeviceto recordresults

sealedreaction flask

magneticstirrer to keepreactantsevenly mixed

water troughbeehive shelf

piece of Mg

Notes:• TimingbegantheinstantIstartedinjectingtheacidfromthesyringeabovetheflaskontothepiece

ofMg.• Thestopwatchwasmountednexttothegraduatedmeasuringcylinder,andthevolumeandtime

wererecordedusingavideoapponatabletdeviceandreplayedinslowmotiontoallowtheresultstobeobtained.

• Theinjectionof20.0mLHClintothesealedreactionflaskimmediatelypushed20.0mLofairoutoftheflaskandintothemeasuringcylinder.IrecordedonlythenetvolumeofH2gasproduced.

c. Identify onefeatureofChris’sexperimentalset-upandnotesabovethatwasdesignedtoimprovetheaccuracyoftheresults.Explainhowthisfeaturecouldimproveaccuracy. 3marks


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Chrisalsorecordedhisobservationsonhisposter.

Observations: Forthe2.0MHCl,initiallytherewasveryrapidbubblingintheflask.Thebubblingslowedovertime.AllMgappearedtohavedissolved.Theflaskbecameveryhot.Forthe1.5Mand1.0MHClsolutions,thebubblingwasnotasrapidasforthe2.0MHCl,andforthe0.5MHClitwasmuchslower.Thesolutionswerestillbubblingwhentimingstopped.Theflasksbecamehot,althoughnotashotastheflaskcontaining2.0MHCl.

d. CommentonChris’sobservations,includingthedifferencesintherateofbubblingandhowwelltheexperimenthadbeencontrolled. 3marks

Chrisreplayedhisvideoinslowmotion,recordedhisexperimentalresultsinhislogbookandproducedagraphforhisposter.Thegraphisshownbelow.

Results:Graph of volume of H2 gas produced against time

2.0 M

1.5 M

1.0 M

0.5 M

Key120

100

80

60

40

20

00 100 200 300

time (s)400 500 600

volumeof H2 gas

(mL)


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e. WhatconclusionsmightChrishavestated,givenhisresultsforthequestionunderinvestigationandhishypothesis? 2marks

f. SuggestoneotherquestionChriscouldasktoextendthisexperimentalinvestigationandbrieflyoutlineanexperimentaldesignthatwouldenableChristoanswerthisquestion.Youmaypresentyouranswerasalistofmainstepsorasasimpleflowchart. 3marks

END OF QUESTION AND ANSWER BOOK

CHEMISTRY (SAMPLE – ANSWERS)

© VCAA 2017 – Version 2 – April 2017

Answers to multiple-choice questions

Question Answer Question Answer

1 D 16 A

2 B 17 B

3 C 18 B

4 C 19 B

5 A 20 D

6 A 21 C

7 D 22 D

8 C 23 A

9 C 24 C

10 A 25 C

11 B 26 C

12 B 27 B

13 B 28 D

14 C 29 A

15 A 30 D

VCE Chemistry – Sample examination...CHEMISTRY (SAMPLE) 2 Version 2 – April 2017 SECTION A ot D...

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Transcript of VCE Chemistry – Sample examination...CHEMISTRY (SAMPLE) 2 Version 2 – April 2017 SECTION A ot D...