【最新!】AP化学真题2015

AP®Chemistry2015Free-ResponseQuestions©2015TheCollegeBoard.CollegeBoard,AdvancedPlacementProgram,AP,APCentral,andtheacornlogoareregisteredtrademarksoftheCollegeBoard.VisittheCollegeBoardontheWeb:®CHEMISTRYEQUATIONSANDCONSTANTSThroughouttheexamthefollowingsymbolshavethedefinitionsspecifiedunlessotherwisenoted.L,mL=liter(s),milliliter(s)mmHg=millimetersofmercuryg=gram(s)J,kJ=joule(s),kilojoule(s)nm=nanometer(s)V=volt(s)atm=atmosphere(s)mol=mole(s)ATOMICSTRUCTUREE=hνc=λνE=energyν=frequencyλ=wavelengthPlanck’sconstant,h=6.626×10−34JsSpeedoflight,c=2.998×108ms−1Avogadro’snumber=6.022×1023mol−1Electroncharge,e=−1.602×10−19coulombEQUILIBRIUMKc=[C][D][A][B]cdab,whereaA+bBRcC+dDKp=CDAB()()()()cdabPPPPKa=[H][A][HA]Kb=[OH][HB][B]Kw=[H+][OH−]=1.0×10−14at25°C=Ka×KbpH=−log[H+],pOH=−log[OH−]14=pH+pOHpH=pKa+log[A][HA]pKa=−logKa,pKb=−logKbEquilibriumConstantsKc(molarconcentrations)Kp(gaspressures)Ka(weakacid)Kb(weakbase)Kw(water)KINETICSln[A]t−ln[A]0=−kt@@0AA11t=ktt½=0.693kk=rateconstantt=timet½=half-life-4-GASES,LIQUIDS,ANDSOLUTIONSPV=nRTPA=Ptotal×XA,whereXA=molesAtotalmolesPtotal=PA+PB+PC+...n=mMK=°C+273D=mVKEpermolecule=12mv2Molarity,M=molesofsoluteperliterofsolutionA=abcP=pressureV=volumeT=temperaturen=numberofmolesm=massM=molarmassD=densityKE=kineticenergyv=velocityA=absorbancea=molarabsorptivityb=pathlengthc=concentrationGasconstant,R=8.314Jmol−1K−1=0.08206Latmmol−1K−1=62.36Ltorrmol−1K−11atm=760mmHg=760torrSTP=273.15Kand1.0atmIdealgasatSTP=22.4Lmolí1THERMODYNAMICS/ELECTROCHEMISTRYq=mc∆T∆S°=productsreactantsSSÇÇDD∆H°=productsreactantsffHHDDÇÇDD∆G°=productsreactantsffGGDDÇÇDD∆G°=∆H°−T∆S°=−RTlnK=−n E°I=qtq=heatm=massc=specificheatcapacityT=temperatureS°=standardentropyH°=standardenthalpyG°=standardGibbsfreeenergyn=numberofmolesE°=standardreductionpotentialI=current(amperes)q=charge(coulombs)t=time(seconds)Faraday’sconstant, =96,485coulombspermoleofelectrons1volt=1joule1coulombCHEMISTRY2015AP®CHEMISTRYFREE-RESPONSEQUESTIONS©2015TheCollegeBoard.VisittheCollegeBoardontheWeb:—1hourand45minutesYOUMAYUSEYOURCALCULATORFORTHISSECTION.Directions:Questions1–3arelongfree-responsequestionsthatrequireabout23minuteseachtoanswerandareworth10pointseach.Questions4–7areshortfree-responsequestionsthatrequireabout9minuteseachtoanswerandareworth4pointseach.Writeyourresponseinthespaceprovidedfollowingeachquestion.Examplesandequationsmaybeincludedinyourresponseswhereappropriate.Forcalculations,clearlyshowthemethodusedandthestepsinvolvedinarrivingatyouranswers.Youmustshowyourworktoreceivecreditforyouranswer.Payattentiontosignificantfigures.1.Metal-aircellsarearelativelynewtypeofportableenergysourceconsistingofametalanode,analkalineelectrolytepastethatcontainswater,andaporouscathodemembranethatletsinoxygenfromtheair.Aschematicofthecellisshownabove.Reductionpotentialsforthecathodeandthreepossiblemetalanodesaregiveninthetablebelow.HalfReactionEatpH11and298K(V)O2(g)+2H2O(l)+4e−→4OH−(aq)+0.34ZnO(s)+H2O(l)+2e−→Zn(s)+2OH−(aq)–1.31Na2O(s)+H2O(l)+2e−→2Na(s)+2OH−(aq)–1.60CaO(s)+H2O(l)+2e→Ca(s)+2OH(aq)−−–2.782015AP®CHEMISTRYFREE-RESPONSEQUESTIONS©2015TheCollegeBoard.VisittheCollegeBoardontheWeb:(a)Earlyformsofmetal-aircellsusedzincastheanode.Zincoxideisproducedasthecelloperatesaccordingtotheoverallequationbelow.2Zn(s)+O2(g)→2ZnO(s)(i)Usingthedatainthetableabove,calculatethecellpotentialforthezinc-aircell.(ii)TheelectrolytepastecontainsOH−ions.Onthediagramofthecellabove,drawanarrowtoindicatethedirectionofmigrationofOH−ionsthroughtheelectrolyteasthecelloperates.(b)Afreshzinc-aircellisweighedonananalyticalbalancebeforebeingplacedinahearingaidforuse.(i)Asthecelloperates,doesthemassofthecellincrease,decrease,orremainthesame?(ii)Justifyyouranswertopart(b)(i)intermsoftheequationfortheoverallcellreaction.(c)Thezinc-aircellistakentothetopofamountainwheretheairpressureislower.(i)Willthecellpotentialbehigher,lower,orthesameasthecellpotentialatthelowerelevation?(ii)Justifyyouranswertopart(c)(i)basedontheequationfortheoverallcellreactionandtheinformationabove.(d)Metal-aircellsneedtobelightweightformanyapplications.Inordertotransfermoreelectronswithasmallermass,NaandCaareinvestigatedaspotentialanodes.A1.0ganodeofwhichofthesemetalswouldtransfermoreelectrons,assumingthattheanodeistotallyconsumedduringthelifetimeofacell?Justifyyouranswerwithcalculations.(e)TheonlycommonoxideofzinchastheformulaZnO.(i)WritetheelectronconfigurationforaZnatominthegroundstate.(ii)FromwhichsublevelareelectronsremovedwhenaZnatominthegroundstateisoxidized?2015AP®CHEMISTRYFREE-RESPONSEQUESTIONS©2015TheCollegeBoard.VisittheCollegeBoardontheWeb:(g)(molarmass28.1g/mol),maybepreparedbythedehydrationofethanol,C2H5OH(g)(molarmass46.1g/mol),usingasolidcatalyst.Asetupforthelabsynthesisisshowninthediagramabove.Theequationfor