CHEMISTRY Candidate session number STANDARD LEVEL PAPER 3€¦ · STANDARD LEVEL PAPER 3...

32 pages

N11/4/CHEMI/SP3/ENG/TZ0/XX

Tuesday 8 November 2011 (morning)

CHEMISTRY

STANDARD 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

Examination code

8 8 1 1 – 6 1 0 6

Candidate session number

0 1 3 2

88116106

–2– N11/4/CHEMI/SP3/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.

(i) Describethree principlesofAAspectroscopy. [3]

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(This question continues on the following page)

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(Question A1 continued)

(ii) Besides thedetectionof calcium ions inblood,wateror soil samples, state twoother uses ofAA spectroscopy. Your answer should list the detection of twodifferentmetalions,eachfromadifferentsource. [1]

Metal ion Source

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

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

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

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

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(iii) ExplainhowastudentcandeterminetheconcentrationofametalioninsolutionusingAAspectroscopy. [2]

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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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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) Statethenamesoftwofunctionalgroupspresentinbothtestosteroneandprogesterone. [2]

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(c) Statethenameofonefunctionalgrouppresentinbothestradiolandtestosterone. [1]

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(d) Explainthreedifferentwaysoralcontraceptivestakenbywomenpreventpregnancy. [3]

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B4. Starchandcellulosearepolysaccharidesfoundinmanyplants.

(a) Comparethestructuresofstarchandcellulose. [3]

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(b) Explainwhyhumanscannotdigestcellulose. [1]

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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) Describeastructuralfeatureoflow-densitypolyethene(LDPE)thatexplainswhyLDPEhasadifferentmeltingpointfromthatofHDPE. [4]

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(c) 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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Option D — Medicines and drugs

D1. Medicinesanddrugsarenaturalorsyntheticsubstancesusedfortheireffectsonthebody.

(a) Listtwogeneraleffectsofmedicinesanddrugsonthefunctioningofthebody. [1]

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(b) Describetheplaceboeffectandstateitsimportanceindrugdevelopment. [2]

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D2. Medicinesareclassifiedbytheeffecteachhasonthebodyandthemind.Onesuchexampleisdepressants.

(a) Describeoneeffectofdepressantsonthehumanbodywhenamoderatedoseisusedandonewhenahighdoseisused. [2]

Moderatedose:

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Highdose:

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(b) Breathalysersuseacidifiedpotassiumdichromate(VI)tooxidizeanyethanolvapourinanindividual’sbreathtoethanoicacid.

(i) Deducethehalf-equationfortheoxidationofethanolwithwatertoformethanoicacidandhydrogenions. [1]

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(ii) Deduce the half-equation for the reduction of acidified dichromate(VI) ions toCr3+(aq)andwater. [1]

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(c) Statetwoothermethodsthatcandetectethanolinthehumanbody. [1]

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D3. 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 D3 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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D4. 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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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,stateonemethodineachcasefortheremovalofnitrogendioxideandsulfurdioxidefromemissiongasesbeforetheyentertheatmosphere. [2]

Nitrogendioxide:

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Sulfurdioxide:

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(c) Both of these air pollutants also contribute to acid deposition. State one chemicalequationforeachgastodescribehoweachformsanacidicsolution. [2]

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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. In many countries the reserves of fresh water are scarce, so fresh water is obtained fromseawater.Antigua,forexample,producesmuchofitsfreshwaterbyreverseosmosiswhereastheUAEproducesmuchofitsfreshwaterthroughmulti-stagedistillation.

Evaluate these two processes. Your answer should include at least one advantage andonedisadvantageforeachprocess. [4]

Advantagedistillation:

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Disadvantagedistillation:

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Advantagereverseosmosis:

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Disadvantagereverseosmosis:

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E4. Ozoneisanaturallyoccurringcomponentofthestratosphere.Theozonelayeroccursinthestratosphereabout30kmabovethesurfaceoftheEarth.

Stratosphericozoneisindynamicequilibriumwithoxygenandiscontinuallybeingformedanddecomposed.

(a) State the condition needed for the depletion of ozone in the stratosphere bynaturalprocesses.Statethetwochemicalequationsfortheprocess. [3]

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(b) Statethenamesoftwoozone-depletingpollutantsandstatetheirsources. [2]

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Option F — Food chemistry

F1. Ahealthydietconsistsofarangeoffoodgroupsintherightproportionsthatprovidetheenergyforthebodytofunction,growandrepairitself.

(a) Statetheempiricalformulaandstructuralfeaturesofmonosaccharides. [2]

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(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]

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(Question F1 continued)

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

(i) DeducethenumberofC=Cbondspresentinonemoleculeofeachfattyacid. [2]

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

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

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

(ii) Deducetheleaststableofthethreefattyacidsandexplainyourreasoning. [2]

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F2. Foodshelf life is the timeit takesforaparticularfoodstuff tobecomeunsuitableforeatingbecauseitnolongermeetscustomerorregulatoryexpectations.Asaresult,inmanypartsoftheworld,packagedfoodshaveadatebeforewhichtheyshouldbeconsumed.

(a) Statethemeaningofthetermrancidityasitappliestofats. [1]

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(b) Rancidityinlipidsoccursbyhydrolyticandoxidativeprocesses.

(i) Comparethetworancidityprocesses. [2]

Hydrolyticprocess:

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

Oxidativeprocess:

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

2 5 3 2

(Question F2 continued)

(ii) Stateoneexampleofafoodcontaininglipidsthatundergoeshydrolyticrancidityandonethatundergoesoxidativerancidity. [2]

Hydrolyticrancidity:

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

Oxidativerancidity:

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

2 6 3 2

–27–

Turn over

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:

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

Maillardreactionequation:

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

2 7 3 2

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

Benefit:

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

Concern:

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

2 8 3 2

–29–

Turn over

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]

2 9 3 2

(Question G1 continued)

(iii) ExplainwhyBisthemajorproductformedinthereactionofAwithHBr. [2]

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

(b) CompoundCcanbeconverteddirectlytocompoundA. Identifythereagentusedforthisconversion. [1]

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

3 0 3 2

–31–

Turn over

(Question G1 continued)

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

potassiumdichromate(VI).

(i) DeducethestructuralformulaofD. [1]

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

(iii) Explain themechanism for the reactionofDwithhydrogencyanide to formF,usingcurlyarrowstorepresentthemovementofelectronpairs. [4]

3 1 3 2

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

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

G3. Benzene,C6H6,isthesimplestaromatichydrocarbon.

Describeandexplainthestructureofbenzene. [3]

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

3 2 3 2

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