AJC_ H1 chem Paper 2

AJC,H1lChemlPaper2\2008l 1l Section A Answerl all lquestionslinlthislsectionlinlthelspaceslprovided.l l 1 (a) Writelalcompletelequationltolrepresentlthelfirstlio nizationlenergylofllithium.l l l l l [1] l l l l (b) (i)l l l l l l l l UsinglthelDatalBooklet,llistlthelfirstlionizationle nergiesloflthelalkalil metals,llithium,lsodiumlandlpotassiumlinltheltablel below.lll Elementl Firstlionizationlenergyl/l kJlmol ,1l Lithiuml l Sodiuml l Potassiuml l l (ii)l Explainltheltrendlobserved.l l l l l l l l l l l l l l l l l [2] l l l l (c) Sodiuml hydride,l NaH,l isl al solidl ofl highl meltingl poi ntl (800 oC)l whereasl hydrogenlfluoride,lHF,lislalgaslatlroomltemperature .l l l (i)l Statel howl thesel twol hydridesl differl inl theirl bo ndingl andl suggestl al reasonlforlthisldifference.l l l l l l l l l l l l l l l (ii)l Drawl dot,and,crossl diagramsl tol showl thel differ entl electronl arrangementslinltheltwolcompounds.l l l l l l l l l l l l [4] l l [Total : 7]

AJC,H1lChemlPaper2\2008l 2l 2 Benzenelandlmethylbenzenelareladdedltolpetrollas lanti,knockingladditiveslinlunleadedl petrol.lAsltheylarelcarcinogenic,lthelamountsloflth eselaromaticlhydrocarbonslinl petrollarelstrictlylregulatedlinlSingapore. l l l l (a) (i)l Bothlbenzenelandlmethylbenzenelreactlwithlbromi nelinltheldarklatl60 oC.lGivel thelnameloflthislreactionlandlthelconditionlrequire dlforlitltoloccur.l l l l l l l l l l l l l (ii)l l l l l l l l Describelonelsimpleltest,tubelreactionlyoulcouldlca rryloutltoldistinguishl methylbenzenelfromlbenzene.lStatelclearlylwhatlwoul dlbelseenlwithleachl compound,landlwritelbalancedlequationslwherelapprop riate.l l l l l l l l l l l [5] l l l l (b) (i)l Whenlburntlinlallimitedlsupplyloflair,lbenzenel formslalmixtureloflcarbon,l carbonlmonoxidelandlwater.lWritelalbalancedlequatio nlforlthelreaction.l l l l l l l l l l (ii)l Completelcombustionlofl1lmoleloflbenzenelunder lstandardlconditionslevolvesl 3276lkJloflheat.lTheldiagramlbelowlshowslanlenergyl cyclelinvolvinglbenzene.l l l l l l l l l l l l l l Uselthelenergylcyclelandlthelthermochemicalldatalb elowltolcalculatelthel standardlenthalpylchangeloflformationloflbenzene.l l enthalpylchangeloflformationloflcarbonldioxidel=l,3 93lkJlmol ,1lll enthalpylchangeloflcombustionloflhydrogenllllll=l,2 86lkJlmol ,1lll +7½lO 2(g)l+7½lO 2(g)l 6C(s)llllllll+lllllllll3H 2(g)l 6CO 2(g)lllllll+llllllll3H 2O(l) l C6H6(l)l

AJC,H1lChemlPaper2\2008l 3l 2 (b) (ii)l l l l l l l l l l l l l l l l l l l (iii) l Thelstandardlenthalpylchangeloflformationloflmethyl benzenelisl+55.0lkJlmol ,1.l Withlreferenceltolyourlanswerlinlb(ii),ldeducelthel relativelstabilitiesloflbenzenel andlmethylbenzene.l l l l l l l l l l l l l l l l l l [6] l l (c) Throughltheluseloflunleadedlpetrollandlinstallation loflcatalyticlconverterslinlcarl engines,lthelamountloflleadlandloxidesloflnitrogenl releasedltolthelenvironmentlhasl beenlreduced.lUnfortu