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.lUnfortunatelylexcessiveluseloflpetrol lstilllpolluteslthelenvironment.l Nameltwolotherlgaseouslpollutantslarisinglfromlthel useloflpetrol.l l l l l [1] l l [Total: 12] l l l l l l l l

AJC,H1lChemlPaper2\2008l 4l 3 (a) Thelioniclproductloflwaterlatl25°Clisl1.0l ×l10 –14 lmol 2ldm –6.l (i) CalculatelthelpHlofl2.0l ×l10 –2lmolldm –3lhydrochloriclacid.l l l l l (ii) WhylislthelpHlofl1.0lxl10 –8lmolldm –3lhydrochloriclacidlnotl8?l l l l l [3] l l (b) Forl each loflthelfollowinglreactionsl Alandl B:l l (i) identifyltheltwolacidslpresent;l (ii) suggest,lwithlreasons,lwhichlionlorlmoleculelislthe lstrongerlacid.l AllllllllH 2SO4lll+lllHNO 3llllllllllllHSO 4 −lll+lllH 2NO3 +lllllllllllll Kcl=l1.6lxl10 2lmolldm ,3 l twolacidslpresent:l l strongerlacid:l l reason: l l l l BllllllllCH 3CONH2ll+llNH 3lllllllllllllCH 3CONH−ll+llNH 4 +lllllll Kcl=l3.6lxl10 −9lmolldm −3ll twolacidslpresent:l l strongerlacid:l l reason: l l l [3] l l l

AJC,H1lChemlPaper2\2008l 5l 3 (c) Thelchloridesloflthelelementslsodiumltolaluminiumla llldissolvelinlwaterltolgivel solutionslofldifferentlpHlvalues.ll (i) Writeldownlthelformulalofleachlofltheselchloridesla ndlsuggestlthelpHlvaluesl oflthelresultinglsolutions.l chlorides of formula pH values of the solution sodiuml l l aluminiuml l l siliconl l ll (ii) Explainlthelbehaviourlofltheselchlorideslwithlwater .lGivelbalancedlequationsl wherelappropriate.l l l l l l l [5] l [Total: 11 ]l

AJC,H1lChemlPaper2\2008l 6l 4 Thel Fischer-Tropsch process lislalcatalyzedlchemicallreactionlinlwhichlalmixtur elofl carbonlmonoxidelandlhydrogenlislconvertedlintolliqu idlhydrocarbonsloflvariouslforms.ll nlCOl(g)l+l(2n+1)lH 2l(g)l→lC nH(2n+2) l(l)l+lnlH 2Ol(g)l wherelnlislalpositivelintegerl ThelFischer,TropschlprocesslislinventedlbylGermanlr esearcherslFranzlFischerlandlHansl Tropsch.lThelmostlcommonlcatalystslarelbasedlonliro nlandlcobalt,lalthoughlnickellandl rutheniumlhavelalsolbeenlused.lThelprincipallpurpos eloflthislprocesslisltolproducelal syntheticlpetroleumlsubstitute,ltypicallylfromlcoal ,lforluselaslsyntheticllubricationloillorlasl syntheticlfuel.lThislsyntheticlfuellrunsltrucks,lca rs,landlsomelaircraftlengines.l ThelreactantlmixturelforlthelFischer,Tropschlproces sl(i.e.lCOlandlH 2)lislcalledl synthesis gas .lItlcanlbelproducedlbylpassinglsteamloverlcoallatl altemperaturelofl800l oC.lThisl reactionlislcalledl gasification oflcoal.l l Cl(s)l+lH 2Ol(g)l lH 2l(g)l+lCOl(g)l Atl800l oC,lthelequilibriumlconstant,l Kc,lforlthislreactionlisl14.1.lThelenergylrequirement lforl thelgasificationloflcoallislusuallylprovidedlbylcom bustionloflcoallwithloxygen.l Cl(s)l+lO 2l(g)l→lCO 2l(g)l Itlwaslalconceptlpioneeredlduringlthel1920slinlpetr oleum,poor,coal,richlGermanyltol extractloillfromlcoallandlbecamelcentralltolNazilGe rmany'slwarleffortslwhenlimportslofl petroleumlwerelrestrictedldueltolwar.lItlwaslknownl asl Ersatz loil,landlaccountedlforlnearlyl halfltheltotalloillusedlinlWorldlWarlIIlbylGermany. lCurrently,lonlylalhandfulloflcompaniesl havelcommercialisedltheirlFischer,Tropschltechnolog y.lShelllinlBintulu,lMalaysialandl SasollinlSouthlAfricaluseslthisltechnologyltolprodu celpetrollandldiesellfuel.ll Onlaverage,ltheselcoal,basedlFischer,Tropschlproces slplantslcanlproducelaslmuchlasl7l tonnesloflCO 2lperltonneloflliquidlhydrocarbonlproducts.l l (a) (i) Writelalbalancedlequationlshowinglthelproductionlof loctanelfromlthelFischer, Tropschlprocess.l l l l l [1] l (ii) GivenlthatlthelbondlenergylislCOlisl1074lkJlmol ,1,luselthel Data Booklet l tolcalculatelthelenthalpylchangeloflthelreactionlin l a(i) .l l l l l l l [1] l

AJC,H1lChemlPaper2\2008l 7l (b) l (i) Suggestlanlexpressionlforl Kc forlthelgasificationloflcoallandlstatelitsl units.l l l l l l l l l l l [1] l l (ii) Thelvaluelofl Kc forlthelgasificationloflcoallisl1.7lxl10 ,21 latl25l oC,lpredictl andlexplainlwhetherlthelreactionlislendothermiclorl exothermic.l l l l l l l l l l l l [2] l l (iii) Tolmaximizelthelyieldloflsynthesislgas,lshouldlthel pressureloflthel systemlbelincreasedlorldecreased?lExplain.l l l l l l l l l l l l l l [2] l (c) Thelsynthesislgaslderivedlfromlcoal,ltypicallylhave lalH 2:COlratioloflaboutl0.7.l HoweverlthelideallH 2:COlratiolforlthelFischer,Tropschlprocesslislaboutl 2.l Anlimportantlreactionlcalledlthelwaterlgaslshiftlre actionlislusedltolchangelthel H2:COlratioloflthelsynthesislgaslaslcloselaslpossible ltol2.lThelwaterlgaslshiftl reactionlinvolveslsteamlreactinglwithlcarbonlmonoxi delgasltolproducel hydrogenlandlcarbonldioxidelgaslaslshownlbelow:l H2Ol(g)l+lCOl(g)l→lH 2l(g)l+lCO 2l(g)l l Brieflylexplainlhowldolyoulthinklthelwaterlgaslshif tlreactionlcanlchangelthel H 2:COlratioloflthelsynthesislgas.ll l l l l l l l [1] l

AJC,H1lChemlPaper2\2008l 8l (d) SuggestlonelenvironmentallimpactloflusinglthelFisch er,Tropschlprocessltol producelliquidlhydr