chemistry candidate session number higher level paper 3 · the chlor-alkali industry manufactures...

40 pages

N11/4/CHEMI/HP3/ENG/TZ0/XX

Tuesday 8 November 2011 (morning)

CHEMISTRY

HIGHER LEVEL

PAPER 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.

• Write your answers in the boxes provided.

1 hour 15 minutes

Examination code

8 8 1 1 – 6 1 0 3

Candidate session number

0 1 4 0

88116103

–2– N11/4/CHEMI/HP3/ENG/TZ0/XX

Option A — Modern analytical chemistry

A1. Spectroscopy involves techniques that can identify substances and determine theirconcentrations.

(a) Identify the atomic or molecular processes associated with the UV and microwaveregionsoftheelectromagneticspectrum. [2]

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Microwave:

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(b) Atomicabsorption(AA)spectroscopyisusedforthedetectionofmetalions.

Besides the detection of calcium ions in blood, water or soil samples, state twoother uses of AA spectroscopy. Your answer should list the detection of twodifferentmetalions,eachfromadifferentsource. [1]

Metal ion Source

1. . . . . . . . . . . . calcium. . . . . . . . . . . .

2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . blood. . . . . . . . . . . . .

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A2. (a) One type of molecular vibration that occurs when CO2 molecules are exposed toIRradiationisillustratedinthediagrambelow.

asymmetricstretching

Identify two other types ofmolecular vibrations that occur when CO2 molecules areexposedtoIRradiation.Illustrateyouranswerwithappropriatediagrams. [2]

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(b) Explain which molecular vibration of CO2 in (a) above is IR active and which isIRinactive. [3]

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A3. Nuclearmagnetic resonance (NMR)andmass spectrometry arediagnostic techniquesoftenusedintheidentificationoforganiccompounds.

(a) Deduce two similarities and one difference in the 1HNMR spectra of the twoisomersCH

3COOH,acarboxylicacid,andHCOOCH

3,anester.1HNMRdataaregivenin

Table18oftheDataBooklet. [3]

Similarities:

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Difference:

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(b) Themass spectrumof oneof the two isomers abovehas significant peaks atmass tochargeratiosof15,45and60,whiletheotherisomerhaspeaksat15,29,31and60.Analyse these fragmentation patterns in the twomass spectra in order to distinguishbetweenthetwoisomers. [2]

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(c) Outlinehowthetechniqueofmagneticresonanceimaging(MRI)isusedinbodyscanners. [2]

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A4. Phenolphthalein indicator is colourless in an acidic solution but coloured in an alkalinesolution.Oxybenzonesunscreeniscolourlessinanaqueoussolution.Structuresofthethreespeciesareshownbelow.

Phenolphthaleinindicator,colourlessinanacidicsolution

Phenolphthaleinindicator,colouredinanalkalinesolution

Oxybenzonesunscreen,colourlessinanaqueoussolution

(a) Describe and explain, in terms of the difference in conjugation of double bonds,whyphenolphthaleinindicatorhasdifferentcoloursinacidicandalkalinesolutions. [2]

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(b) In acidic solution, phenolphthalein indicator absorbs from about 230nm to 270nm.Inalkalinesolutionitabsorbsfromabout540nmto560nm.Basedonthestructureofoxybenzonesunscreen,predict andexplain the rangeoverwhich the sunscreenwouldabsorbelectromagneticradiation.UseTable3oftheDataBooklettoarriveatyouranswer. [2]

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A5. Chromatographyinvolvesabroadrangeoftechniquesthatcanbeusedtoseparateandanalysecomplexmixtures.

(a) Explainwhygas-liquidchromatography(GLC)issuitableforthedeterminationofbloodalcohollevelsbutnotfortheseparationofsugarsamples. [2]

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(b) Outlinethetechniqueofhigh-performanceliquidchromatography(HPLC). [4]

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Option B — Human biochemistry

B1. A student carried out an experiment to determine the energy value of 100.00g of a foodproductbyburningsomeofit.A5.00gsamplewasburnedandtheheatproducedwasusedtoheatwaterinaglassbeaker.

Sherecordedthefollowingdata:

Massofwaterheated 100.00 g=

Initialtemperatureofwater 19.2 C°=

Highesttemperatureofwater 28.6 C°=

Otherdata:

Heatcapacityoftheglassbeaker 190.2 J K−=

Specificheatcapacityofwater 1 14.18 J g K− −=

Calculatetheenergyvaluefor100.00gofthefoodproduct,inkJ,showingyourworking. [3]

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B2. Proteinsaremacromoleculesformedfrom2-aminoacids.Onceaproteinhasbeenhydrolysed,chromatographyandelectrophoresiscanbeusedtoidentifytheaminoacidspresent.

(a) State the name of the linkage that is broken during the hydrolysis of a protein anddrawitsstructure. [2]

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(b) Explainhowelectrophoresisisusedtoanalyseaprotein. [4]

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B3. Hormonesare involved inavarietyofdifferentprocesses in thebodyandcanvarygreatlyintheirchemicalcompositionandstructure.ThestructuresofsomehormonesareshowninTable21oftheDataBooklet.

(a) Statethefunctionofhormones. [1]

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(b) Statethenameofonefunctionalgrouppresentinbothestradiolandtestosterone. [1]

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B4. Starchandcellulosearepolysaccharidesfoundinmanyplants.

Comparethestructuresofstarchandcellulose. [3]

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B5. Enzymes are protein molecules that catalyse specific biochemical reactions.Thephosphorylationofglucoseisthefirststepofglycolysis(theoxidationofglucose)andiscatalysedbytheenzymehexokinase.

(a) Explainhowenzymes,suchashexokinase,areabletocatalysereactions. [2]

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(b) State and explain the effect of increasing the temperature from 20 C° to 60 C° on anenzyme-catalysedreaction. [4]

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B6. DNAisthegeneticmaterialthatindividualsinheritfromtheirparents.GeneticinformationisstoredinchromosomeswhichareverylongstrandsofDNA.

(a) DescribethestructureofanucleotideofDNA. [1]

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(b) Outlinehownucleotidesarelinkedtogethertoformpolynucleotides. [1]

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(c) OutlinethestepsinvolvedintheDNAprofilingofabloodsample. [3]

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Option C — Chemistry in industry and technology

C1. TheIndustrialRevolutionwastheresultoflarge-scaleextractionofironfromitsoreandhadsignificantimpactworldwide.

(a) Inablast furnace,a largevolumeofair is introducedunderpressurenear thebottomwhileamixtureoflimestone,cokeandiron(III)oxideisintroducedatthetop.

(i) Statetheequationforthereactionofcokewithairintheblastfurnace. [1]

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(ii) The product formed in part (i) reacts with coke to produce carbon monoxide.Explain,givinganequation,whythisreactionisimportantintheextractionofiron. [2]

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(b) Ironformedintheblastfurnacecontainsabout5%carbon,togetherwithotherimpuritiessuchasphosphorus,siliconandsulfur.Describe,usingequations,thechemicalprinciplebehind the conversionof impure iron into steel using thebasic oxygen converter andexplainhowtheimpuritiesareremoved. [3]

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C2. Sincetheaccidentaldiscoveryofpolyetheneinthe1930s,polymershaveplayedanessentialroleindailylifebecauseoftheirwiderangeofpropertiesanduses.

(a) Titanium compounds are used as catalysts in the manufacture of high-densitypolyethene(HDPE).Discusstwofactorsscientistswouldhaveconsideredinchoosingthesecatalysts. [2]

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(b) Polyurethanes are made from dialcohol (diol) and diisocyanate monomers.Byconsideringthestructuresofthetwomonomersandtherepeatingunitofthepolymergivenbelow,suggestwhy itcouldbeargued that this reaction isnotanexampleofacondensationpolymer. [2]

NNCO C On

HO CH2 CH2 OH+ n

HN NHC

O CH2 CH2 O

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(This question continues on the following page)

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(Question C2 continued)

(c) Kevlarisanotherexampleofacondensationpolymer.ExplainhowthegreatstrengthofKevlardependsonitsstructure. [2]

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(d) Stateoneenvironmentalimpactofthedisposalofthesepolyethenesbyusingincineration. [1]

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C3. Fuel cells convert chemical energy directly into electrical energy that can be used inapplicationsrangingfromspacecrafttoremoteweatherstations.

(a) Describethecompositionoftheelectrodesinahydrogen-oxygenfuelcell. [1]

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(b) Statethehalf-equationateachelectrodeinthehydrogen-oxygenalkalinecell. [2]

Positiveelectrode(cathode):

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Negativeelectrode(anode):

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C4. Itwasoverahundredyearsaftertheaccidentaldiscoveryofliquidcrystalsthatliquid-crystaldisplays (LCDs) came into common use in the 1990s. Liquid crystals are formed over atemperaturerangebetweenthesolidandtheliquidstate.

(a) Describethenematicliquid-crystalphaseintermsofthearrangementofthemolecules. [2]

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(b) Explaintheeffectofincreasingthetemperatureonthenematicliquidcrystal. [2]

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C5. Thechlor-alkaliindustrymanufacturestwoimportantproducts(sodiumhydroxideandchlorine)fromtheelectrolysisofaqueoussodiumchloride.Themembranecellisincreasinglyusedinthisprocess.

(a) (i) Stateeitherthecompositionorthetypeofmembraneusedinthiscell. [1]

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(ii) State the half-equation for the reaction taking place at each electrode in themembranecell. [2]

Positiveelectrode(anode):

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Negativeelectrode(cathode):

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(b) Discuss two reasons why the membrane cell is replacing the mercury-cathode anddiaphragmcellsinthechlor-alkaliindustry. [2]

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Option D — Medicines and drugs

D1. Medicinesanddrugsarenaturalorsyntheticsubstancesusedfortheireffectsonthebody.

(a) Listtwogeneraleffectsofmedicinesanddrugsonthefunctioningofthebody. [1]

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(b) Describetheplaceboeffectandstateitsimportanceindrugdevelopment. [2]

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D2. Stimulants stimulate the brain and the central nervous system and tend to increasealertnessandphysicalactivity.StructuralformulasofsomestimulantsaregiveninTable20oftheDataBooklet.

(a) Comparethestructuresofthetwostimulantsamphetamineandepinephrine(adrenaline). [2]

Similarity:

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Difference:

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(b) Predictandexplainwhichofthesetwostimulantswouldbemorewatersoluble. [2]

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(Question D2 continued)

(c) Caffeineandnicotinearealsostimulants.

(i) Identifythetypeofaminethatispresentinbothcaffeineandnicotine. [1]

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(ii) Deducewhether an aqueous solution of caffeine is acidic, basic or neutral andexplainyourreasoning. [2]

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(iii) Describetwoeffectsofcaffeinewhenitisconsumedinlargeamounts. [1]

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D3. Antibioticstreatinfectionsbystoppingthegrowthofbacteriaordestroyingthem.

(a) Identify the side-chain by drawing a circle around the side-chain in the structure ofbenzyl penicillin given below (the structure of penicillin is given in Table 20 of theDataBooklet). [1]

(b) Discuss two problems associated with the overprescription of penicillin and explainhowtheseareovercome. [3]

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D4. Chiralityplaysanimportantroleintheactionofdrugs.

(a) Usinganasterisk(*),identifythechiralcarbonatominthestructureofthalidomide. [1]

(b) Describethecompositionofaracemicmixture. [1]

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(c) Discusstheimportanceofchiralityindrugactionusingthalidomideastheexample. [2]

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D5. (a) Somedrugscanbeconvertedintoionicsaltsinordertoincreasetheirsolubilityinwater.

(i) Statetheequationfortheformationoftheionicsaltofaspirin,CH3COO(C6H4)COOH. [1]

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(ii) State the equation for the formation of the ionic salt of fluoxetine,F3C(C6H4)OCH(C6H5)CH2CH2NHCH3. [1]

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(b) Chiralauxiliariesareusedindrugdesign.Describehowachiralauxiliaryworks. [2]

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(c) Discussoneargumentforandoneargumentagainstthelegalizationofcannabis. [2]

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Option E — Environmental chemistry

E1. Nitrogendioxideandsulfurdioxidearetwoairpollutants.

(a) Nitrogen dioxide is formed in a two-stage process. Describe one anthropogenic(man-made) source of nitrogen dioxide and state the two chemical equations foritsformation. [2]

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(b) Apartfromusingrenewabletechnologies,state onemethodineachcasefortheremovalofnitrogendioxideandsulfurdioxidefromemissiongasesbeforetheyentertheatmosphere. [2]

Nitrogendioxide:

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Sulfurdioxide:

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(c) Bothoftheseairpollutantsalsocontributetoaciddeposition.OutlinemechanismsfortheformationofHNO

3andSO

3. [4]

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E2. The temperature of the Earth is increasing. There is considerable scientific evidence tosuggest this is due to an increase in the concentration of greenhouse gases as a result ofhumanactivity.

(a) Explain how this enhanced greenhouse effect causes the average temperature of theEarthtoincrease. [3]

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(b) Compare the contributions of carbon dioxide and methane to the enhancedgreenhouseeffect. [2]

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E3. (a) Raw sewage is the water-carried waste that flows away from a community. If it isdischargeduntreatedintoriversandtheseaitcausespollution.Therefore,wastewatershouldbetreatedbeforeitisdischarged.

Phosphate ions are one of the pollutants removed from sewage water by chemicalprecipitationusingcalciumions.

Thesolubilityproduct,Ksp,ofcalciumphosphate,Ca3(PO4)2,is

261.20 10−× at298K.

Determine theconcentrationofphosphate ions, inmoldm–3, ina saturatedsolutionofcalciumphosphate. [3]

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

2 6 4 0

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(Question E3 continued)

(b) Inmanycountriesthereservesoffreshwaterarescarce,sofreshwaterisobtainedfromseawater. Antigua,forexample,producesmuchofitsfreshwaterbyreverseosmosiswhereastheUAEproducesmuchofitsfreshwaterthroughmulti-stagedistillation.

Evaluate these twoprocesses.Your answer should includeat leastone advantageandonedisadvantageforeachprocess. [4]

Advantagedistillation:

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

Disadvantagedistillation:

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Advantagereverseosmosis:

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Disadvantagereverseosmosis:

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2 7 4 0

E4. Soilcanbepollutedbyavarietyofsubstances.

Listtwocommonorganicsoilpollutantsandstatetheirsources. [2]

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

E5. Oneofthewinnersofthe1995NobelPrizeinChemistrywasPaulJ.Crutzen,whoshowedthatemissionsofnitrogenoxidesfromjetairplanescouldcontributetothedestructionoftheozonelayer.

Using chemical equations, outline a mechanism by which nitrogen oxides are able todepleteozone. [3]

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

2 8 4 0

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Option F — Food chemistry

F1. Ahealthydietconsistsofarangeoffoodgroupsintherightproportionsthatprovidetheenergyforthebodytofunction,growandrepairitself.

(a) Statetheempiricalformulaandstructuralfeaturesofmonosaccharides. [2]

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

(b) (i) Statethestructuralformulaof2-aminoethanoicacid. [1]

(ii) Deduce the structural formula of a triester formed from three long-chaincarboxylic acid molecules, RCOOH, and one propane-1,2,3-triol molecule,HO–CH2CH(OH)–CH2OH.Identifyoneoftheesterlinkagesinthestructurebydrawingarectanglearoundit. [2]

2 9 4 0

(Question F1 continued)

(c) Examples of straight-chain fatty acids include C19H39COOH, C19H31COOH andC19H29COOH.

(i) DeducethenumberofC=Cbondspresentinonemoleculeofeachfattyacid. [2]

C19H39COOH: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C19H31COOH: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C19H29COOH: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Deducetheleaststableofthethreefattyacidsandexplainyourreasoning. [2]

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

3 0 4 0

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F2. Theoxidativerancidityreactioninfoodsinvolvesafree-radicalmechanism.Stateanequationforeachofthefollowingsteps,usingRHtorepresentanunsaturatedfattyacid. [3]

Initiation:

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

Propagation:

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Termination:

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3 1 4 0

F3. Thebrowningoffoodduringcookingiscausedbytwodifferentprocesses,caramelizationandnon-enzymaticbrowning (Maillard reaction). Theseprocesses lead toapleasantcolourandflavourinavarietyoffoodproducts.Inthefoodslistedbelow,assumethefollowingformulas:

• Sugar:C6H12O6

• Reducingsugar:HOCH2(CH(OH))4CHO

• Aminoacid:H2N–CHR–COOH

ComparethetwobrowningprocesseswithrespecttothechemicalcompositionofthefoodsaffectedandstatethechemicalequationfortheMaillardreaction. [4]

Chemicalcompositionoffoodsthatundergothecaramelizationprocess:

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

Chemicalcompositionoffoodsthatundergothenon-enzymaticbrowningprocess:

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Maillardreactionequation:

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

3 2 4 0

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F4. Foods derived from genetically modified organisms were introduced in the early 1990s.Stateonebenefitandoneconcernofconsuminggeneticallymodifiedfoods. [2]

Benefit:

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

Concern:

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3 3 4 0

F5. Stereochemistry is thestudyof thespatialarrangementofatoms inmolecules. Amoleculecontainingachiralcarbonatomexistsastwoenantiomers.Threedifferentconventionscanbeusedfornamingpurposes.

(a) Use the CORN rule to determine whether the structure of 2-aminopropanoic acid(alanine)representstheDorLform.Justifyyouranswer. [2]

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

(b) Statethe(d)orthe(l)convention. [1]

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

3 4 4 0

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F6. Afoodproductisoftenjudgedsimplybyitscolour.Naturalpigmentsthatgiverisetofoodcolour include anthocyanins, carotenes, chlorophyll and heme. The structures of thesepigmentsareshowninTable22oftheDataBooklet.

(a) Explainwhythesenaturalpigmentsarecoloured. [2]

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

(b) Deduce from their structures whether anthocyanins and carotenes are water-solubleorfat-soluble. [2]

Anthocyanins:

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Carotenes:

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Option G — Further organic chemistry

G1. ConsiderthefollowingreactionpathwaystartingwithcompoundAwhichisbut-1-ene.

3CH2CH=CH2Õ BÕCH

3CH2CHOHCH3

ÕD A C

(a) (i) A reacts with HBr to form amajor and aminor product. Draw the structuralformulasofthesetwoisomers. [1]

(ii) ExplainthemechanismofthereactionofAwithHBrtoformthemajorproduct,B,usingcurlyarrowstorepresentthemovementofelectronpairs. [4]

3 6 4 0

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(Question G1 continued)

(iii) ExplainwhyBisthemajorproductformedinthereactionofAwithHBr. [2]

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

(b) (i) CompoundCcanbeconverteddirectlytocompoundA.Identifythereagentusedforthisconversion. [1]

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

(ii) StatethechemicalequationforthereactionofcompoundCwithethanoylchloride,CH

3COCl, and draw the structural formula of the organic product formed in

thisreaction. [2]

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

3 7 4 0

(c) CompoundD, molecular formula C4H8O, is formedwhenC is heated with acidified

potassiumdichromate(VI).

(i) CompoundD reactswith2,4-dinitrophenylhydrazine,H2NNH–C6H3(NO2)2,togiveasolidE.DeducethestructuralformulaofE. [1]

(ii) Compound D reacts with the Grignard reagent methylmagnesium bromide,CH

3MgBr,andwatertogivetheorganicproductF.Deducethestructuralformula

ofF. [1]

(iii) State thenameof the typeofmechanismwhenD reactswithhydrogencyanidetoproduceG. [1]

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

(iv) DeducethestructuralformulaoftheorganicproductformedwhenGishydrolysedbyanacid. [1]

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G2. By referring to Table 15 of the Data Booklet, compare and explain the relative basicitiesofammonia,methylamineanddimethylamine. [3]

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G3. Benzene, C6H6, reacts with bromomethane, CH3Br, under appropriate conditions, to form

methylbenzene,C6H5CH3.

(a) Explain the mechanism for the reaction of benzene with bromomethane, using curlyarrowstorepresentthemovementofelectronpairs. [3]

3 9 4 0

(b) Both benzene and methylbenzene undergo electrophilic substitution reactions tosynthesizeothercompounds.

(i) Deducethestructuralformulaofoneorganicproductformedwhenmethylbenzenereactswithbrominebyelectrophilicsubstitution. [1]

(ii) Compareandexplaintherelativeratesoftheelectrophilicsubstitutionreactionofbenzeneandmethylbenzenewithbromine. [4]

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4 0 4 0

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