chemistry higher level paper 2 past papers... · wednesday 12 may 2010 (afternoon) chemistry higher...

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M10/4/CHEMI/HP2/ENG/TZ2/XX

Wednesday 12 May 2010 (afternoon)

CHEMISTRYHIGHER lEvElPaPER 2

INSTRUCTIONS TO CANDIDATES

• Write your session number in the boxes above.• Do not open this examination paper until instructed to do so.• Section A: answer all of Section A in the spaces provided.• Section B: answer two questions from Section B. Write 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 numbers of the questions answered in the candidate box on your cover sheet and indicate the number of sheets used in the appropriate box on your cover sheet.

2 hours 15 minutes

Candidate session number

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© International Baccalaureate Organization 2010

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Section a

Answer all the questions in the spaces provided.

1. Thepercentagebymassofcalciumcarbonate ineggshellwasdeterminedbyaddingexcesshydrochloricacidtoensurethatallthecalciumcarbonatehadreacted.Theexcessacidleftwasthentitratedwithaqueoussodiumhydroxide.

(a) Astudentadded27.20cm3of0.200moldm–3HClto0.188gofeggshell.Calculatetheamount,inmol,ofHCladded.

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(b) The excess acid requires 23.80cm3 of 0.100moldm–3 NaOH for neutralization.Calculatetheamount,inmol,ofacidthatisinexcess.

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(c) Determine the amount, in mol, of HCl that reacted with the calcium carbonate intheeggshell.

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(d) StatetheequationforthereactionofHClwiththecalciumcarbonateintheeggshell.

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[2]

(e) Determinetheamount,inmol,ofcalciumcarbonateinthesampleoftheeggshell.

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[2]

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(Question 1 continued)

(f) Calculate the mass and the percentage by mass of calcium carbonate in theeggshellsample.

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(g) Deduceoneassumptionmadeinarrivingatthepercentageofcalciumcarbonateintheeggshellsample.

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[1]

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2. (a) Drawandlabelanenergyleveldiagramforthehydrogenatom.Inyourdiagramshowhow the series of lines in the ultraviolet and visible regions of its emission spectrumareproduced,clearlylabellingeachseries. [4]

(b) On theabovediagram,drawthe line thatcorresponds to thefirst ionizationenergyofhydrogenandexplainyourreasoning.

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[2]

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3. Considerthebondingandstructureoftheperiod3elements.

(a) Explaintheincreaseinthemeltingpointfromsodiumtoaluminium.

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[2]

(b) Explainwhysulfur,S8,hasahighermeltingpointthanphosphorus,P4.

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(c) Explainwhysiliconhasthehighestmeltingpointandargonhasthelowestmeltingpoint.

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[2]

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4. One important property of a rocket fuel mixture is the large volume of gaseous productsformedwhichprovidethrust.Hydrazine,N2H4,isoftenusedasarocketfuel.Thecombustionofhydrazineisrepresentedbytheequationbelow.

N H g O g N g H O g kJmolc2 4 2 2 212 585( ) ( ) ( ) ( )+ → + ∆ = − −H Ö

(a) Hydrazine reacts with fluorine to produce nitrogen and hydrogen fluoride, all in thegaseousstate.Stateanequationforthereaction.

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[2]

(b) DrawtheLewisstructuresforhydrazineandnitrogen. [2]

(c) UsetheaveragebondenthalpiesgiveninTable10oftheDataBooklettodeterminetheenthalpychangeforthereactioninpart(a)above.

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[3]


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(d) Basedonyouranswerstoparts(a)and(c),suggestwhetheramixtureofhydrazineandfluorineisabetterrocketfuelthanamixtureofhydrazineandoxygen.

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[2]

(e) CommentontheenvironmentalsafetyoftheproductsofthereactionofN2H4withO2andthereactionofN2H4withF2.

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5. Existenceofisomersleadstodiversityoforganiccompounds.

(a) Describewhatismeantbythetermstereoisomers.

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(b) 1,3-dichlorocyclobutaneexistsasgeometricalisomers,aformofstereoisomers.

(i) Drawandnamethetwogeometricalisomersof1,3-dichlorocyclobutane.

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[2]

(ii) Identifytheisomerwiththehigherboilingpointandexplainyourreasoning.

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Section B

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

6. Theperiodictableshowstherelationshipbetweenelectronconfigurationandthepropertiesofelementsandisavaluabletoolformakingpredictionsinchemistry.

(a) Identifythepropertyusedtoarrangetheelementsintheperiodictable. [1]

(b) (i) Definethetermelectronegativity. [2]

(ii) Outlinetworeasonswhyelectronegativityincreasesacrossperiod3intheperiodictableandonereasonwhynoblegasesarenotassignedelectronegativityvalues. [3]

(c) (i) Outlinetworeasonswhyasodiumionhasasmallerradiusthanasodiumatom. [2]

(ii) ExplainwhytheionicradiusofP3–isgreaterthantheionicradiusofSi4+. [2]


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(d) Thegraphbelowrepresentsthesuccessiveionizationenergiesofsodium.Theverticalaxis plots log (ionization energy) insteadof ionization energy to allow thedata to berepresentedwithoutusinganunreasonablylongverticalaxis.

logIE

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.01 2 3 4 5 6 7 8 9 10 11

Numberofelectronsremoved

Statethefullelectronconfigurationofsodiumandexplainhowthesuccessiveionizationenergydataforsodiumarerelatedtoitselectronconfiguration. [4]

(e) (i) Explain why the first ionization energy of aluminium is lower than the firstionizationenergyofmagnesium. [2]

(ii) Explainwhythefirstionizationenergyofsulfurislowerthanthefirstionizationenergyofphosphorus. [2]

(f) Thetenelementsinthefirst-rowd-blockhavecharacteristicpropertiesandmanyuses.

(i) State andexplain the typeof reaction that takesplacebetweenFe3+ andH2O toform[Fe(H2O)6]

3+intermsofacid-basetheories. [2]

(ii) Explainwhy[Fe(H2O)6]3+iscoloured. [3]

(iii) Outline the economic significance of the use of a catalyst in theHaber processwhichisanexothermicreaction. [2]

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7. (a) WaterisanimportantsubstancethatisabundantontheEarth’ssurface.

(i) Statetheexpressionfortheionicproductconstantofwater,Kw. [1]

(ii) ExplainwhyevenaveryacidicaqueoussolutionstillhassomeOH–ionspresentinit. [1]

(iii) StateandexplaintheeffectofincreasingtemperatureonthevalueofKwgiventhattheionizationofwaterisanendothermicprocess. [3]

(iv) StateandexplaintheeffectofincreasingtemperatureonthepHofwater. [2]

(b) BuffersolutionsresistsmallchangesinpH.AphosphatebuffercanbemadebydissolvingNaH2PO4andNa2HPO4inwater,inwhichNaH2PO4producestheacidicionandNa2HPO4producestheconjugatebaseion.

(i) Deduce theacidandconjugatebase ions thatmakeup thephosphatebufferandstatetheionicequationthatrepresentsthephosphatebuffer. [3]

(ii) Describe how the phosphate buffer minimizes the effect of the addition of astrongbase,OH–(aq),tothebuffer.Illustrateyouranswerwithanionicequation. [2]

(iii) Describe how the phosphate buffer minimizes the effect of the addition of astrongacid,H+(aq),tothebuffer.Illustrateyouranswerwithanionicequation. [2]

(c) A0.10moldm–3ammoniasolutionisplacedinaflaskandtitratedwitha0.10moldm–3

hydrochloricacidsolution.

(i) ExplainwhythepHoftheammoniasolutionislessthan13. [2]

(ii) EstimatethepHattheequivalencepointforthetitrationofhydrochloricacidwithammoniaandexplainyourreasoning. [2]

(iii) State the equation for the reaction of ammonia with water and write the KbexpressionforNH3(aq). [2]

(iv) Whenhalftheammoniahasbeenneutralized(thehalf-equivalencepoint),thepHofthesolutionis9.25.Deducetherelationshipbetween[NH3]and[NH4

+]atthehalf-equivalencepoint. [1]

(v) DeterminepKbandKbforammoniabasedonthepHatthehalf-equivalencepoint. [3]

(vi) Describethesignificanceofthehalf-equivalencepointintermsofitseffectivenessasabuffer. [1]

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8. The word redox comes from a combination of the terms reduction and oxidation.Redoxreactionsaffectourdailylives.

(a) Theoverallreactionthattakesplaceinavoltaiccellisshownbelow.

Pb (s PbO (s 2H SO (aq PbSO (s H O(l2 2 4 4 2) ) ) ) )+ + → +2 2

(i) DeterminetheoxidationnumberofleadinPb,PbO2andPbSO4. [1]

(ii) Deducetheoxidationandreductionhalf-equationstakingplaceatthenegativeleadelectrode(anode)andthepositivelead(IV)oxideelectrode(cathode).Deducetheoxidizingandreducingagentsandstatethedirectionoftheelectronflowbetweentheelectrodes. [4]

(iii) Inordertodeterminethepositionofthreemetalsinareactivityseries,themetalswere placed in different solutions of metal ions. The table below summarizeswhetherornotareactionoccurred.

ag+(aq) cu2+(aq) Pb2+(aq)ag (s) Noreaction Noreaction

cu (s) Reaction Noreaction

Pb (s) Reaction Reaction

Statetheequationsforthethreereactionsthattakeplace.UsethisinformationtoplacethemetalsAg,CuandPbinareactivityseries,withthestrongestreducingagentfirst,andexplainyourreasoning. [5]

(iv) UseinformationfromTable14oftheDataBooklettodeducetheoxidizingagentthatcanoxidizechlorideionsbutnotfluorideions.Statetheredoxequationforthereactionanddetermineitscellpotential. [4]

(b) (i) Molten sodium chloride is electrolysed in a cell using inert electrodes.State the half-equation, with state symbols, for the reaction taking place atthe positive electrode (anode) and for the reaction taking place at the negativeelectrode(cathode).Determinethemoleratiooftheproductsformed. [3]

(ii) Predict and explain the products of electrolysis of a concentrated solution ofNaCl(aq)usinginertelectrodes.Youranswershouldincludehalf-equationswithstatesymbolsforthereactionateachelectrode. [4]


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(c) Electroplating is an important application of electrolytic cells with commercialimplications.Coppermaybeplatedusinganelectrolyticcellwithanaqueousacidifiedcopper(II)sulfateelectrolyte.

Forthecopperplatingoftintomakejewellery,statethehalf-equationateachelectrode.Assumetheotherelectrodeisalsoinert. Suggesttwoobservationsthatyouwouldbeabletomakeastheelectroplatingprogresses. [4]

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9. (a) Alkenesareaneconomicallyandchemicallyimportantfamilyoforganiccompounds.

(i) The reaction of alkenes with bromine water provides a test for unsaturationin the laboratory. Describe the colour change when bromine water is addedtochloroethene. [1]

(ii) Deduce the Lewis structure of chloroethene and identify the formula of therepeatingunitofthepolymerpoly(chloroethene). [2]

(iii) Besidespolymerization,statetwocommercialusesofthereactionsofalkenes. [2]

(b) Halogenoalkanes undergo two major types of reaction leading to the formation ofdifferentorganiccompounds.

(i) 1-bromopropanecanbeconverted to1-butylamine(butan-1-amine) intwo stages.Drawthestructuralformulasof1-bromopropaneand1-butylamine(butan-1-amine). [1]

(ii) Deduce a reaction pathway for the two-stage conversion of 1-bromopropane to1-butylamine(butan-1-amine).Youranswershouldincludeanequationforeachstageofthereactionandthereactionconditionsforthesecondstage. [4]

(c) (i) DescribetheeliminationofHBrfrombromoethane.Youranswershouldincludethereagents,conditionsandequationforthereaction. [3]

(ii) ExplainthemechanismfortheeliminationofHBrfrombromoethane. [5]

(d) But-2-enecanbeconvertedtobutan-2-oneintwostages.

(i) Drawthestructuralformulasofbut-2-eneandbutan-2-one. [2]

(ii) Deduceareactionpathwayforthetwostagesofthereaction.Youranswershouldincludethefullybalancedequationforeachstageofthereactionandthereagentsandconditionsforthetwostages. [5]

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chemistry higher level paper 2 past papers... · wednesday 12 may 2010 (afternoon) chemistry higher...

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