化學(xué)專業(yè)英語試題及答案1.Whenconductingatitrationanalysistodeterminetheconcentrationofhydrochloric

acid(HCl)usingsodiumhydroxide(NaOH)asthetitrant,whichofthefollowing

indicatorswouldbemostsuitablefordetectingtheequivalencepoint,giventhatthe

reactionproduceswaterandsodiumchloride(NaCl)asproducts,andthepHatthe

equivalencepointisapproximately7?()A.Phenolphthalein(changescoloratpH8.2-10.0)B.Methylorange(changescoloratpH3.1-4.4)C.Bromothymolblue(changescoloratpH6.0-7.6)D.Litmuspaper(changescoloratpH4.5-8.3)Answer:C2.Inthesynthesisofaspirin(acetylsalicylicacid)fromsalicylicacidandacetic

anhydride,thereactioniscatalyzedbysulfuricacid(H2SO4).Whichofthefollowing

statementscorrectlydescribestheroleofsulfuricacidinthisesterificationreaction?()

A.Itactsasanucleophiletoattacktheaceticanhydride.B.Itservesasadehydratingagenttoremovewaterformedduringthereaction.

C.Itprotonatesthecarbonyloxygenofaceticanhydride,makingitmoreelectrophilic.

D.Itdirectlyreactswithsalicylicacidtoformanintermediate.

Answer:C3.Duringthedistillationofamixturecontainingethanolandwater,whichofthe

followingfactorswouldmostsignificantlyaffecttheseparationefficiencyofthetwo

components,consideringtheirdifferentboilingpoints(ethanol:78.4°C,water:100°C)?

()A.Therateofheatingappliedtothedistillationflask.

B.Thepresenceofairbubblesinthedistillationcolumn.

C.Thelengthandpackingmaterialofthefractionaldistillationcolumn.

D.Theinitialvolumeratioofethanoltowaterinthemixture.

Answer:C4.Whenanalyzingthepurityofasynthesizedorganiccompoundusingthin-layer

chromatography(TLC),astudentobservesmultiplespotsontheTLCplateunder

ultravioletlight,eventhoughthereactionwassupposedtoproduceasingleproduct.

Whichofthefollowingexplanationsisthemostlikelycauseforthisobservation?()

A.ThesolventusedforTLCdevelopmentwastoopolar.B.Thesamplewascontaminatedwithunreactedstartingmaterialsorby-products.

C.TheTLCplatewasnotproperlyactivatedbeforeuse.D.Theultravioletlampusedforvisualizationwasmalfunctioning.

Answer:B5.Inthecontextofelectrochemistry,whenazincelectrodeisimmersedinazincsulfate

solutionandacopperelectrodeisimmersedinacoppersulfatesolution,connectedbya

saltbridgeandanexternalcircuit,whichofthefollowingstatementsaccuratelydescribes

theflowofelectronsintheexternalcircuitduringtheoperationofthisgalvaniccell?()

A.Electronsflowfromthecopperelectrodetothezincelectrode.B.Electronsflowfromthezincelectrodetothecopperelectrode.C.Noelectronflowoccursbecausebothelectrodesareintheirstandardstates.

D.Electronsflowbackandforthbetweentheelectrodesduetoequilibrium.

Answer:B6.AchemististaskedwithpreparingabuffersolutionwithapHof4.5usingaceticacid(pKa=4.76)anditsconjugatebase,sodiumacetate.WhichofthefollowingratiosofaceticacidtosodiumacetatewouldbemostappropriatetoachievethedesiredpH,accordingtotheHenderson-Hasselbalchequation?()A.1:1B.2:1C.1:2D.1:1.8Answer:D7.Duringtheextractionofcaffeinefromtealeavesusingdichloromethaneastheorganic

solvent,astudentnoticesthattheorganiclayer(containingcaffeine)appearscloudyafter

separation.Whichofthefollowingstepswouldbethemosteffectiveinclarifyingthe

organiclayertoensureapurecaffeineextract?()A.Addingmorewatertothemixture.B.Filteringtheorganiclayerthroughapadofanhydroussodiumsulfate.

C.Re-extractingtheaqueouslayerwithfreshdichloromethane.

D.AdjustingthepHofthemixturetobasicconditions.Answer:B8.Whenperformingagravimetricanalysistodeterminethesulfurcontentinacoal

samplebyprecipitatingsulfurasbariumsulfate(BaSO4),whichofthefollowing

precautionsismostcriticaltoensureaccurateresults,consideringpotentialinterferences

fromotherelementsinthecoal?()A.Usingexcessbariumchloride(BaCl2)toensurecompleteprecipitation.

B.MaintainingalowpHduringprecipitationtopreventtheformationofothermetal

sulfates.C.Washingtheprecipitatewithdistilledwatertoremoveimpurities.

D.Ignitingtheprecipitatetoconstantweightbeforeweighing.

Answer:B9.Inthelaboratorysynthesisofbenzocaine(ananesthetic),thereactionbetweenp-

aminobenzoicacidandethanoliscatalyzedbysulfuricacid.Whichofthefollowing

safetymeasuresismostimportantwhenhandlingsulfuricacidduringthisreactionto

preventaccidents?()A.Wearingglovesmadeoflatex.B.Usingafumehoodtoavoidinhalationofvapors.

C.Addingsulfuricacidslowlytothereactionmixturewithstirring.

D.Storingsulfuricacidinaclearglassbottleforeasyvisibility.

Answer:C10.Astudentistaskedwithdeterminingtheconcentrationofiron(III)ionsinawater

sampleusingspectrophotometry.Afterpreparingaseriesofstandardsolutionsand

measuringtheirabsorbances,thestudentconstructsacalibrationcurve.However,the

absorbancereadingsfortheunknownsamplefalloutsidethelinearrangeofthe

calibrationcurve.Whichofthefollowingactionswouldbethemostappropriateto

accuratelydeterminetheiron(III)concentrationintheunknownsample?()

A.Dilutingtheunknownsampleandre-measuringitsabsorbance.B.Usingadifferentwavelengthforspectrophotometricmeasurements.

C.Increasingtheconcentrationofthestandardsolutions.D.Ignoringthedataandestimatingtheconcentrationvisually.Answer:A11.WhensynthesizingaGrignardreagent(e.g.,phenylmagnesiumbromide)from

bromobenzeneandmagnesiummetalinananhydrousethersolvent,whichofthe

followingconditionsisabsolutelyessentialtopreventthereactionfromfailing?()

A.Usingalargeexcessofbromobenzenerelativetomagnesium.B.Ensuringthereactionvesseliscompletelydryandfreeofmoisture.

C.Addingasmallamountofiodineasacatalyst.D.Stirringthereactionmixturevigorouslythroughoutthereaction.

Answer:B12.Inthecontextofpolymerchemistry,duringthefree-radicalpolymerizationofstyrene

toformpolystyrene,whichofthefollowinginitiatorswouldbemostsuitablefor

initiatingthepolymerizationreactionatroomtemperaturewithouttheneedforexternal

heating?()A.Benzoylperoxide(requiresheattodecompose)B.Azobisisobutyronitrile(AIBN,decomposesatelevatedtemperatures)

C.Potassiumpersulfate(requiresreductiontoinitiate)

D.Aredoxsysteminvolvingammoniumpersulfateandsodiummetabisulfite

Answer:D13.Achemistisanalyzingthecrystalstructureofanewlysynthesizedcompoundusing

X-raydiffraction.Duringthedatacollectionprocess,thechemistnoticesthatthe

diffractionpeaksarebroadandpoorlyresolved.Whichofthefollowingadjustmentsto

theexperimentalsetupwouldbemostlikelytoimprovetheresolutionofthediffraction

peaks?()A.IncreasingthewavelengthoftheX-raysource.B.DecreasingtheangleofincidenceoftheX-raysonthecrystal.

C.Usingahigher-qualitycrystalwithfewerdefects.D.Reducingtheexposuretimetopreventdetectorsaturation.

Answer:C14.Whenperformingarecrystallizationtopurifyacrudeorganiccompound,astudent

observesthattherecoveredcrystalsaresmallandpowderyratherthanlargeandwell-

formed.Whichofthefollowingmodificationstotherecrystallizationprocedurewouldbe

mosteffectiveinpromotingthegrowthoflarger,moredesirablecrystals?()

A.Increasingtherateofcoolingofthehotsaturatedsolution.B.Usingalargervolumeofsolventrelativetotheamountofcrudecompound.

C.Addingasmallamountofaseedcrystalofthedesiredproducttothesolution.

D.Stirringthesolutionvigorouslyduringthecoolingprocess.Answer:C15.Inthesynthesisofacoordinationcompound,suchas[Cu(NH3)4]SO4,which

involvesthereactionofcopper(II)sulfatewithexcessammoniasolution,whichofthe

followingobservationswouldindicatethatthereactionhasproceededtocompletionand

thedesiredproducthasbeenformed?()A.Thesolutionchangesfrombluetocolorless.B.Aprecipitateformsandthenredissolvesuponadditionofmoreammonia.

C.Thesolutionremainsblue,buttheintensityofthecolordecreases.

D.Bubblesofgasareevolvedduringthereaction.Answer:B16.Duringthepreparationofasoap(sodiumstearate)bythesaponificationofstearic

acidwithsodiumhydroxide,whichofthefollowingconditionswouldmostlikelyleadto

theformationofasoft,greasysoapratherthanahard,solidsoap?()A.Usinganexcessofstearicacidrelativetosodiumhydroxide.B.Conductingthereactionatatemperaturebelowthemeltingpointofstearicacid.

C.Usingadilutesolutionofsodiumhydroxideinsteadofaconcentratedone.

D.Addingsalt(sodiumchloride)tothereactionmixtureduringoraftersaponification.

Answer:C17.Astudentisperformingacolumnchromatographyseparationofamixtureoftwo

dyes,oneredandoneblue,usingsilicagelasthestationaryphaseandahexane-ethylacetatemixtureasthemobilephase.Ifthereddyeelutesfirst,followedbythebluedye,

whichofthefollowingstatementscorrectlydescribestherelativepolaritiesofthetwo

dyesbasedontheirelutionorder?()A.Thereddyeismorepolarthanthebluedye.B.Thebluedyeismorepolarthanthereddye.C.Bothdyeshavethesamepolaritybutdifferentmolecularweights.

D.Thepolarityofthedyescannotbedeterminedfromtheirelutionorder.

Answer:B18.Whenanalyzingthecompositionofagasmixtureusinggaschromatography,a

studentobservestwodistinctpeaksonthechromatogram,correspondingtotwodifferent

gases.Iftheretentiontimeofthefirstpeakis2.5minutesandtheretentiontimeofthe

secondpeakis5.0minutes,whichofthefollowingstatementsismostaccurateregarding

thevolatilityofthetwogases?()A.Thegascorrespondingtothefirstpeakismorevolatilethanthegascorrespondingto

thesecondpeak.B.Thegascorrespondingtothesecondpeakismorevolatilethanthegascorresponding

tothefirstpeak.C.Bothgaseshavethesamevolatilitybutdifferentboilingpoints.

D.Thevolatilityofthegasescannotbedeterminedfromtheirretentiontimes.

Answer:A19.Inthelaboratorysynthesisofibuprofen,thereactionbetweenisobutylbenzeneand

aceticacidinthepresenceofaLewisacidcatalyst(e.g.,aluminumchloride)proceedsvia

aFriedel-Craftsacylationmechanism.Whichofthefollowingintermediatespeciesis

formedduringthisreactionbeforethefinalproduct,ibuprofen,isobtained?()

A.Acarbocationintermediateonthebenzenering.B.Atetrahedralintermediateinvolvingtheaceticacidmolecule.

C.Aradicalintermediategeneratedbyhomolyticcleavage.D.Acoordinationcomplexbetweenthereactantsandthecatalyst.

Answer:A20.Whenperformingameltingpointdeterminationofapurifiedorganiccompound,a

studentrecordsameltingpointrangeof149-151°C,whichisslightlylowerthanthe

literaturevalueof152-154°Cforthesamecompound.Whichofthefollowing

explanationsisthemostlikelycauseforthisdiscrepancy?()A.Thecompoundisstillimpure,containingtraceamountsofothersubstances.

B.Themeltingpointapparatuswasnotcalibratedcorrectly.C.Thesamplewasnotgroundintoafinepowderbeforepackingintothecapillarytube.

D.Theheatingrateduringthemeltingpointdeterminationwastoofast.

Answer:A21.Inthecontextofenvironmentalchemistry,whenanalyzingwatersamplesforthe

presenceofheavymetalssuchaslead(Pb)andcadmium(Cd)usingatomicabsorption

spectroscopy(AAS),whichofthefollowingsamplepreparationstepsismostcriticalto

ensureaccurateandsensitivedetectionofthesemetalsatlowconcentrations?()

A.Filteringthewatersampletoremovesuspendedsolids.B.Acidifyingthewatersamplewithnitricacidtopreventmetalprecipitation.

C.Dilutingthewatersampletobringthemetalconcentrationswithinthelinearrangeof

theAAS.D.Addingachelatingagenttocomplexthemetalsandenhancetheirabsorption.

Answer:B22.Achemististaskedwithsynthesizingachiralcompoundandneedstoseparatethe

enantiomers(opticalisomers)oftheproduct.Whichofthefollowingchromatographic

techniqueswouldbemostsuitableforthisseparation,consideringtheuniqueproperties

ofenantiomers?()A.Thin-layerchromatography(TLC)onaregularsilicagelplate.

B.Gaschromatography(GC)withanon-chiralstationaryphase.

C.High-performanceliquidchromatography(HPLC)withachiralstationaryphase.

D.Paperchromatographyusingapolarsolventsystem.Answer:C23.Duringthesynthesisofabiodieselfromvegetableoilandmethanolinthepresenceofabasecatalyst(e.g.,sodiumhydroxide),whichofthefollowingby-productsisformedinadditiontothebiodiesel(fattyacidmethylesters)?()A.Glycerol

B.WaterC.Carbondioxide

D.EthanolAnswer:A24.Whenperformingaredoxtitrationtodeterminetheconcentrationofiron(II)ionsina

solutionusingpotassiumpermanganate(KMnO4)asthetitrant,whichofthefollowing

indicatorsisnotnecessarybecausethereactionitselfprovidesavisualendpointdueto

thecolorchangeofthepermanganateion?()A.PhenolphthaleinB.MethylorangeC.Starch(usediniodometrictitrations)D.Noindicatorisneeded;thepinkcolorofexcessKMnO4signalstheendpoint.

Answer:D25.Astudentissynthesizingametalcomplexbyreactingatransitionmetalsalt(e.g.,

nickel(II)chloride)withabidentateligand(e.g.,ethylenediamine).Afterthereactioniscomplete,thestudentisolatesapurplesolid.Whichofthefollowinganalyticaltechniques

wouldbemostusefulinconfirmingtheidentityandpurityofthesynthesizedmetal

complex?()A.Infraredspectroscopy(IR)toidentifyfunctionalgroupsintheligand.

B.Nuclearmagneticresonancespectroscopy(NMR)todeterminethestructureofthe

complex.C.X-raydiffraction(XRD)todeterminethecrystalstructureofthecomplex.

D.Alloftheabovetechniqueswouldbeusefulindifferentways.

Answer:D26.Inthelaboratorypreparationofhydrogengasbythereactionofzincmetalwithdilute

sulfuricacid,whichofthefollowingsafetyprecautionsismostimportanttoprevent

accidents,especiallyconsideringtheflammabilityofhydrogen?()

A.Wearingsafetygogglestoprotecttheeyesfromacidsplashes.

B.Conductingthereactioninawell-ventilatedareaorfumehood.

C.Usingagascollectionapparatusthatpreventsbackflowofairintothereactionvessel.

D.Addingthezincmetalslowlytotheacidtocontrolthereactionrate.

Answer:C27.Whenanalyzingthekineticsofachemicalreactionbymonitoringthechangein

concentrationofareactantorproductovertime,whichofthefollowinggraphical

methodswouldbemostappropriatefordeterminingtheorderofthereactionwithrespect

toaparticularreactant?()A.Plottingtheconcentrationofthereactantversustime.B.Plottingthenaturallogarithmoftheconcentrationofthereactantversustime.

C.Plottingthereciprocaloftheconcentrationofthereactantversustime.

D.Alloftheaboveplotsmaybeusefuldependingonthereactionorder.

Answer:D28.Achemistisworkingwithahighlyreactiveandtoxicgas,suchashydrogencyanide(HCN),inthelaboratory.Whichofthefollowingpersonalprotectiveequipment(PPE)itemsismostcriticalforthechemisttowearwhenhandling