chemistry standard level paper 3cdochemistrychristman.pbworks.com/w/file/fetch/80645057/10... ·...

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M10/4/CHEMI/SP3/ENG/TZ1/XX+

Thursday 13 May 2010 (morning)

CHEMISTRYSTANDARD lEvElPAPER 3

INSTRUCTIONS TO CANDIDATES

• Write your session number in the boxes above.• Do not open this examination paper until instructed to do so.• Answer all of the questions from two of the Options in the spaces provided. You may continue

your answers on answer sheets. Write your session number on each answer sheet, and attach them to this examination paper and your cover sheet using the tag provided.

• At the end of the examination, indicate the letters of the Options answered in the candidate box on your cover sheet and indicate the number of answer sheets used in the appropriate box on your cover sheet.

1 hour

Candidate session number

2 2 1 0 6 1 1 2

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Option A — Modern analytical chemistry

A1. Butan-1-ol, butan-2-ol, 2-methylpropan-1-ol and 2-methylpropan-2-ol are four structuralisomerswiththemolecularformulaC4H10O.

(a) Detailsofthe1HNMRspectraoftwoofthesealcoholsaregivenbelow.

Spectrum 1 Twopeaks: Oneat1.3ppm(relativetotheTMSreference)withanintegrationtraceof

nineunits,andtheotherat2.0ppmwithanintegrationtraceofoneunit.

Spectrum 2 Fourpeaks: Thefirstat0.9ppmwithanintegrationtraceofsixunits.

Thesecondat1.7ppmwithanintegrationtraceofoneunit. Thethirdat2.1ppmwithanintegrationtraceofoneunit. Thefourthat3.4ppmwithanintegrationtraceoftwounits.

Consider the proton environments present in each of the alcohol molecules whenansweringthefollowingquestions.

(i) Identifywhichalcoholgivesspectrum1andexplainyouranswerbystatingwhichhydrogenatomsinthemoleculeareresponsibleforeachofthetwopeaks.

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(ii) Deducewhichalcoholgivesspectrum2.Explainwhichparticularhydrogenatomsinthemoleculeareresponsibleforthepeaksat0.9ppmand3.4ppm.

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(This question continues on the following page)

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(Question A1 continued)

(b) Themassspectrumofoneofthealcoholsshowspeaksatm/zvaluesof74,59and45.

(i) Deducewhich twoof thealcoholscouldproduce this spectrumand identify thespeciesresponsibleforthethreepeaks.

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(ii) Thespectrumalsoshowsasignificantpeakatm/z=31. Suggestwhichalcoholis responsible for this spectrumanddeduce the species responsible for thepeakatm/z=31.

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(c) Explainwhytheinfraredspectraofallfouralcoholsareverysimilar.

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A2. Atomic absorption spectroscopy can be used to determine the concentration of lead ions in acontaminatedsampleofdrinkingwater.

(a) Stateoneotheruseofatomicabsorptionspectroscopy.

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(b) Describethefunctionofeachofthefollowinginanatomicabsorptionspectrophotometer.

Thefuel:

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Theatomizer:

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Themonochromaticlightsource:

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(Question A2 continued)

(c) Acalibrationcurvewasplottedusingwaterwithknownconcentrationsofleadions.Absorbance

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

ConcentrationofPb2+(aq)/mgdm–3

100dm3 of the contaminated drinking water was reduced by boiling, to 7.50dm3.Itwas found thatwhen the reduced volumewas tested it had an absorbance of 0.55.Calculate the concentration of lead ions (in mgdm–3) in the original contaminateddrinkingwater.

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Option B — Human biochemistry

B1. Individual2-aminoacidshavedifferentstructuresdependingonthepHofthesolutiontheyaredissolvedin.ThestructuresofserineandcysteinearegiveninTable19oftheDataBooklet.

(a) Deducethestructureofserinein

(i) asolutionwithapHof2. [1]

(ii) asolutionwithapHof12. [1]

(b) Deducethestructureofserineattheisoelectricpoint. [1]

(c) Deduce the structures of the two different dipeptides that can be formed when onemoleculeofserinereactswithonemoleculeofcysteine. [2]

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(Question B1 continued)

(d) Thetertiarystructuresofproteinsmadeupof2-aminoacidresiduessuchasserineandcysteine,aretheresultofinteractionsbetweenaminoacidstogiveathree-dimensionalshape.Statefivedifferenttypesofinteractionthatcanoccur,ineachcaseidentifytheatomsorgroupsjoinedtogether.

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B2. (a) Statethecausesofthethreedeficiencydiseases,beriberi,goitreandpellagra.

Beriberi:

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Goitre:

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Pellagra:

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(b) Suggest three ways in which society can solve the problems associated withmalnutrition.

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B3. UnsaturatedfatscontainC=Cdoublebonds.Theamountofunsaturationinafatoroilcanbedeterminedbytitratingwithiodinesolution.

(a) Definethetermiodine number .

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(b) Linoleicacid(Mr=281)hasthefollowingformula.

CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH

Calculate the volume of 1.00moldm–3 iodine solution required to react exactlywith1.00goflinoleicacid.

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Option C — Chemistry in industry and technology

C1. (a) Explainwhyironisobtainedfromitsoresusingchemicalreducingagentsbutaluminiumisobtainedfromitsoresusingelectrolysis.

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(b) Bothcarbonmonoxideandhydrogencanbeusedtoreduceironores.Statetheequationsforthereductionofmagnetite,Fe3O4,with

(i) carbonmonoxide.

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(ii) hydrogen.

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(c) Explainwhymuchoftheironproducedinablastfurnaceisconvertedintosteel.

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(d) State thematerials used for the positive and negative electrodes in the production ofaluminiumbyelectrolysis.

Positiveelectrode:

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Negativeelectrode:

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(Question C1 continued)

(e) Aluminium is one of themost abundant elements foundonEarth. Discusswhy it isimportanttorecyclealuminium.

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C2. (a) Usehigh-densitypoly(ethene)andlow-densitypoly(ethene)asexamplestoexplainthedifferencethatbranchingcanmaketothepropertiesofapolymer.

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(b) During the formation of poly(styrene), a volatile hydrocarbon such as pentane isoftenadded.Describehowthisaffectsthepropertiesofthepolymerandgiveoneuseforthisproduct.

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C3. (a) Statethedifferencebetweenhomogeneousandheterogeneouscatalysts.

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(b) State one advantage and one disadvantage that homogeneous catalysts have overheterogeneouscatalysts.

Advantage:

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Disadvantage:

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(c) Apartfromtheirselectivitytoformtherequiredproductandtheircost,discusstwootherfactorswhichshouldbeconsideredwhenchoosingasuitablecatalystforanindustrialprocess.

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Option D — Medicines and drugs

D1. Aspirin,paracetamol(acetaminophen),morphineanddiamorphine(heroin)areallpainkillers.TheirstructuresaregiveninTable20oftheDataBooklet.

(a) Aspirinisthoughttointerferewiththeproductionofprostaglandins.Explainhowthisproducesananalgesiceffect.

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(b) Explainhowmorphinecanpreventpain.

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(c) Paracetamol(acetaminophen) isgenerallyconsideredtobesafe touseasananalgesicinsmalldoses.Otherthanthepossibilityofdeath,outlinetheproblemsassociatedwithtakinglargerdosesofparacetamol.

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(d) Stateoneimportantuseforaspirinotherthanthereliefofpainandfever.

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(e) Other than the phenyl group, state the name of one other functional group that iscommonto

(i) bothparacetamolandmorphine.

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(ii) bothaspirinanddiamorphine.

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(Question D1 continued)

(f) Explainwhatismeantbythetermtoleranceandsuggestwhythisisaparticularproblemforheroinusers.

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D2. Thefirstpenicillintobeusedwasbenzylpenicillin(PenicillinG),itsstructureisshownbelow.

(a) Explainhowpenicillinsareabletoactasantibacterials.

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(b) Modern penicillins have a similar structure to PenicillinG but a different side-chain.Statetwoadvantagesofmodifyingtheside-chain.

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(c) Discuss the reasonwhya“cocktail”ofdifferentantibacterialsmaybeneeded to treattuberculosis(TB).

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D3. (a) Sodiumhydrogencarbonate,NaHCO3,andmagnesiumhydroxide,Mg(OH)2,canbothbeusedasantacids.

(i) Givetheequationsforthereactionsofsodiumhydrogencarbonateandmagnesiumhydroxidewithhydrochloricacid.

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(ii) Compare the effectiveness of 1.00g of sodium hydrogencarbonate to 0.50g ofmagnesiumhydroxideincombatingacidityinthestomach.

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(b) Explainwhyalginatesareoftenaddedtoantacids.

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Option E — Environmental chemistry

E1. (a) Two primary air pollutants are carbon monoxide and oxides of nitrogen. State oneman-madesourceforeachofthesepollutants.

Carbonmonoxide:

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Oxidesofnitrogen:

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(b) Explainhowacatalyticconverterworksandgivetheequationforthecatalysedreactionbetweencarbonmonoxide,CO,andnitrogenmonoxide,NO.

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(c) Stateone other type of primary pollutant, other than carbonmonoxide and oxides ofnitrogen,thatcanalsoberemovedfromtheairbyacatalyticconverter.

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(d) Particulatesmaybeproducedbytheburningoffossilfuels.Explainhowsmallparticulatescanberemovedfromtheexhaustgasesofcoal-burningpowerstationsbeforetheyentertheatmosphere.

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E2. (a) Thedisposalofalltypesofwasteisanincreasingproblem.Onemethodofremovingwasteisincineration.Stateoneadvantageandonedisadvantageofincineratingwaste.

Advantage:

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Disadvantage:

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(b) Statethecharacteristicsandsourcesoflow-levelnuclearwaste.

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(c) Thedisposalofnuclearwasteintheseaisnowbannedinmanycountries.Discussonemethodofstoringhigh-levelnuclearwasteandtwoproblemsassociatedwithit.

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E3. (a) Stratospheric ozone is in dynamic equilibriumwith oxygen. Give the equations thatdescribetheformationofozonefromoxygenanditsdepletioninthestratosphereinthepresenceofultravioletlight.

Formation:

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Depletion:

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(b) SincetheMontrealProtocolin1987,theuseofozone-depletingCFCshasalmostbeenphasedout.Discussoneadvantageandtwodisadvantagesofusinghydrocarbonssuchas2-methylpropaneasareplacementforCFCs.

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Option F — Food chemistry

F1. Simplesugarsarenutrientsandarealsodescribedasmonosaccharides.

(a) Distinguishbetweenafoodandanutrient .

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(b) Statethreecharacteristicfeaturesofallmonosaccharidemolecules.

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(c) Explain the chemistry behind the non-enzymatic browning reaction that occurswhenmakingfudgefromsugarandcream.

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F2. (a) Explainwhypigmentssuchasanthocyaninsarecoloured.

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(b) Thewavelengthofvisiblelightliesbetween400and750nm.Theabsorptionspectrumofaparticularanthocyaninisshownbelow.

Intensityofabsorption

400 450 500 550 600 650Wavelength/nm

(i) Explainwhateffect,ifany,theabsorptionat375nmwillhaveonthecolouroftheanthocyanin.

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(ii) Explainwhateffect,ifany,theabsorptionat530nmwillhaveonthecolouroftheanthocyanin.

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(c) Listtwofactorswhichcouldaltertheprecisecolourofaparticularanthocyanin.

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λ =530 nm

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F3. (a) Givethegeneralstructuralformulaforafatoroilanddescribethedifferenceinstructurebetweenasaturatedandanunsaturatedfattyacid.

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(b) Explainwhyunsaturatedfatshavealowermeltingpointthansaturatedfats.

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(c) Oilscanbehydrogenated.Onepossibleproblemisthatpartialhydrogenationmayoccurwhich produces an oil containing trans fatty acids. Explain the structural differencebetweenacisfattyacidandatransfattyacidandstateonedisadvantageofingestingoilscontainingtransfattyacids.

Difference:

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Disadvantage:

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Option G — Further organic chemistry

G1. Whenbromoethanereactswithmagnesiuminthepresenceofanon-polarsolvent,aGrignardreagentisformed.

(a) GivetheequationforthereactionofthisGrignardreagentwithwater.

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(b) ThisGrignardreagentcanalsoreactwithaldehydesandketonestogiveaninitialproductwhichcanthenbehydrolysedbywatertoformanalcohol.StatethenamesandformulasofthealcoholsformedwhentheGrignardreagentreactswith

(i) ethanal.

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(ii) propanone.

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–25–

Turn over

(Question G1 continued)

(c) Alcohols can undergo elimination reactions in the presence of hot concentratedphosphoricacid.

(i) Name the organic product formed when butan-1-ol undergoes an eliminationreaction.

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(ii) Explainthemechanismforthiseliminationreactionusingcurlyarrowstorepresentthemovementofelectronpairs. [3]

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G2. Alkenescanundergoelectrophilicadditionreactionswithbromineandwithhydrogenbromide.

(a) Explainhowabrominemoleculeisabletoactasanelectrophile.

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(b) Nametheproductformedwhenbut-2-enereactswith

(i) bromine.

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(ii) hydrogenbromide.

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(c) Whenbut-1-enereactswithhydrogenbromide,twopossibleorganicproductscouldbeformedbutinpracticeonlyoneorganicproductisobtainedinhighyield.Explainthemechanismfor this reactionusingcurlyarrows torepresent themovementofelectronpairsandexplainclearlywhyonlyoneorganicproductisformed.

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G3. Benzeneissometimesrepresentedascontainingthreealternatedoubleandsinglebonds(Fig.1)andsometimesrepresentedasahexagonwithacircleinthemiddle(Fig.2).

Fig.1 Fig.2

(a) Describe two different types of physical evidencewhich show that benzene does notcontainthreedoublebonds.

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(b) Explain how the reaction of benzene with bromine provides chemical evidence thatbenzenedoesnotcontainthreedoublebonds.

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2 7 2 7

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