2010 A-level H2 Chem Suggested solutions _Oct 2011.pdf
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2010 A-level H2 Chem Suggested solutions _Oct 2011.pdf

2010A-levelH2ChemSuggestedsolutions_Oct2011_.pdf

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SuggestedSolnsforN2010H2ChemistryPaper1(9746/01)1234567891011121314151617181920BBBDBCAADABDCBCBCCBC2122232425262728293031323334353637383940DBBDDABCCDABABCBCAACWorkingforSuggestedSolnsforN2010H2ChemistryPaper1(9746/01)Q1PElementBrKKrSc3bp&1lpabtPcentralatomCovalent0.1140.196(covalent0.1170.144oHHBondangle=107Radius/nmradius)(inH0.227(metallicKrF2)Ans:Bradius)RadiiofKandKrarederivedfrom“S.I.ChemicalQ6rdData”ByG.Aylward&T.Findlay3ed,WileyIoniclatticestructureofMgOisheldbyelectrostaticPublisher.forcesofattractionbetweenoppositelychargedions,Directapplicationoftrend.Atomicradiishouldfallthusoppositelychargedionsmustbenexttoeachacrosstheperiodwithincreasingeffectivenuclearothertominimizerepulsionbetweenlikechargedcharge.Thisisbecauseacrosstheperiod,nuclearions.chargeincreasesbutshieldingeffectdoesnotAns:Cincreaseassignificantly.ThusKhasthelargestatomicradius.(note:KrformscompoundsanditsQ7covalentradiuscanbedetermined.HaditbeenNH3hasthemoresignificantandstrongestperiod2or3,NeandArwillbeobservedtohaveanintermolecularinteractions(hydrogenbonding)anomalouslylargeradiusastheydonotformamongstthe4gasesofthe4options.Theother3compounds,andvanderWaalsradiiaremeasuredgasesarenon-polarcovalentsimplemolecules,thusinstead.)theyhavevanderWaals’forcesofinteractions.Ans:BAns:A731.1×10dm5Q8TheconcepthereisbondbreakingalwaysQ2AmtofCO2==4.91×10molrequiresenergy(endothermic)andbondformation22.4dm3alwaysreleasesenergy(exothermic)since3molofCO2gives2molofNa2CO3(A)Enthalpychangeofatomisation,ΔHatm,involves54.91×105theliberationofgaseousatomsfromelementsAmtofNa2CO3=×2=3.27×10mol3instandardstates.Thismeansbreakingofbondsbetweenatomsisalwaystheonlyprocessinvolved,thusatomizationmustMassofNa2CO3alwaysbeendothermic=(3.27××++105)mol(2(23.0)12.03(16.0))g/mol7(B)Enthalpychangeofcombustion,ΔHC,isthe=3.47×10genthalpychangewhenonemoleofsubstanceAns:Bundergoescompletecombustioninexcessoxygen.BondsarebrokeninoxygenandtheQ3substance,andformedintheproducts.