AP 化学 BONDING.docx

AP 化学 BONDING.docx

《AP 化学 BONDING.docx》由会员分享，可在线阅读，更多相关《AP 化学 BONDING.docx（46页珍藏版）》请在冰豆网上搜索。

AP化学BONDING

TheAdvancedPlacementExaminationinChemistry

PartII-FreeResponseQuestions&Answers

1970to2009

Bonding&MolecularStructure

Teachersmayreproducethispublication,inwholeorinpart,inlimitedprintquantitiesfornon–commercial,face–to–faceteachingpurposes.Thispermissiondoesnotapplytoanythird–partycopyrightscontainedwithinthispublication.

AdvancedPlacementExaminationinChemistry.Questionscopyright©1970–2009bytheCollegeEntranceExaminationBoard,Princeton,NJ08541.Reprintedwithpermission.Allrightsreserved..Thismaterialmaynotbemassdistributed,electronicallyorotherwise.Thispublicationandanycopiesmadefromitmaynotberesold.

Portionscopyright©1993–2009by

UnlimitedPotential,Framingham,MA01701–2619.

CompiledfortheMacintoshandPCby:

HarveyGendreau（ret.）

FraminghamHighSchool

Framingham,MA01701

419–735–4782（fax）

508–877–8723（homeoffice）

apchemtchr@

hgendreau@

RequestsforcopiesofthesequestionsandanswersinMS-OfficeformatfortheMacintoshandPC（MS–Wordfiles）shouldbesentto:

apchemtchr@

Pleaseincludeyourname,school,schoolphone,nameofprincipal/headmasterandschoolURLaddress.

1973D

Discussbrieflytherelationshipbetweenthedipolemomentofamoleculeandthepolarcharacterofthebondswithinit.Withthisasthebasis,accountforthedifferencebetweenthedipolemomentsofCH2F2andCF4.

Answer:

Inordertohaveadipolemoment（i.e.,tobeapolarmolecule）amoleculemusthavepolarbondsandmusthaveamoleculargeometrywhichisnotsymmetrical（i.e.,oneinwhichthevectorsumofthebonddipoles0）.

InCH2F2theC-FandC-Hbondsarepolarandthemoleculeisnotsymmetrical;therefore,themoleculesispolarandwouldshowadipolemoment.

InCF4theC-Fbondsarepolar,butthemoleculeissymmetrical;therefore,themoleculeisnon-polarandwouldnotshowadipolemoment.

1974D

ThepossiblestructuresforthecompounddinitrogenoxideareNNOandNON.Byexperimentationithasbeenfoundthatthemoleculeofdinitrogenoxidehasanon-zerodipolemomentandthationsofmass44,30,28,16,and14areobtainedinthemassspectrometer.Whichofthestructuresissupportedbythesedata?

Showhowthedataareconsistentwiththisstructure.

Answer:

ThecorrectstructureisNNO.N-N=O;N-Obonddi-pole;non-linearstructure,non-symmetrical;moleculardipolemoment.

SpectralData（massofmolecularfragments）:

44=NNO28=NN14=N30=NO16=O

Afragmentof28couldn’tbemadeifthestructurewasNON.

1974D

Theboilingpointsofthefollowingcompoundsincreaseintheorderinwhichtheyarelistedbelow:

CH4

Discussthetheoreticalconsiderationsinvolvedandusethemtoaccountforthisorder.

Answer:

CH4-weakLondondispersion（vanderWaals）forces

H2S-Londonforces+dipole-dipoleinteractions

NH3-London+dipole+hydrogenbonding

1975D

SupposethatamoleculehastheformulaAB3.Sketchandnametwodifferentshapesthatthismoleculemayhave.Foreachofthetwoshapes,giveanexampleofaknownmoleculethathasthatshape.Foroneofthemoleculesyouhavenamed,interprettheshapeinthecontextofamodernbondingtheory.

Answer:

Example:

trigonalplanar,BF3;trigonalpyramid,NH3

ForBF3,theboronatomissurroundedbythreepairsofelectrons,thearrangementthatwillminimizetherepulsionsisaflat（planar）arrangementwiththeelectronpairsfurthestapartat120ºangles.OR

TheNH3moleculehasfourpairsofelectrons:

threebondingpairsandonenon-bondingpair.Thebestarrangementforfourelectronpairsisatetrahedralstructure（109.5º）withthelone（non-bonding）electronpairattheapexrequiringmorespacethanthebondingpairs,compressingthebondingpairstoanangleof107º.Themolecularstructureisalwaysbasedonthepositionsoftheatoms,thereforeitisatrigonalpyramidratherthanatetrahedron.

1976D

NF3andPF5arestablemolecules.Writetheelectron-dotformulasforthesemolecules.Onthebasisofstructuralandbondingconsiderations,accountforthefactthatNF3andPF5arestablemoleculesbutNF5doesnotexist.

Answer:

Describethesp3bondingforNF3andthesp3dforPF5.

NonexistenceofNF5becauseofnolowenergydorbitalforN.

1978D

Statepreciselywhatismeantbyeachofthefollowingfourterms.Thendistinguishclearlybetweeneachofthetwotermsinpart（a）andbetweeneachofthetwotermsinpart（b）,usingchemicalequationsorexampleswherehelpful.

（a）Bondpolarityandmolecularpolarity（dipolemoment）

（b）ForametalM,ionizationenergyandelectrodepotential.

Answer:

（a）Bondpolarity-resultingfromunequalsharingofelectronsbetweenbondingatoms;orfrombondingofatomswithdifferentelectronegativities.

Molecularpolarity-resultoftheseparationofthecentersofpositiveandnegativechargesinanentiremolecule（Thedipolemomentisameasure）.;ortheresultofthenon-zerovectorsumofbonddipolesandlone-pairelectrons.

Distinction（normallyincludedwithinthedefinitions）.

（b）Ionizationenergy-energyrequiredtoremoveanelectronfromanatom[ifatomisdescribedasgaseousorisolated-1additionalpoint]

Electrodepotential-relatedtoenergyassociatedwithoxidationorreductionorassociatedwithatendencytogainorloseelectrons.

Aquantitymeasuredrelativetothehydrogenelectrodeorrelatedtotheenergychangesinanelectrochemicalcell.

Distinction（normallyincludedwithinthedefinitions）.

1979D

DrawLewisstructuresforCO2,H2,SO3andSO32-andpredicttheshapeofeachspecies.

Answer:

1979D

Butane,chloroethane,acetone,and1-propanolallhaveapproximatelythesamemolecularweights.Dataontheirboilingpointsandsolubilitiesinwaterarelistedinthetablebelow.

Compound

Formula

BoilingPt.（ºC）

Solubilityinwater

Butane

CH3CH2CH2CH3

0

insoluble

Chloroethane

CH3CH2Cl

12

insoluble

Acetone

CH3C

CH3

56

completelymiscible

1-Propanol

CH3CH2CH2OH

97

completelymiscible

Onthebasisofdipolemoments（molecularpolarities）and/orhydrogenbonding,explaininaqualitativewaythedifferencesinthe

（a）boilingpointsofbutaneandchloroethane.

（b）watersolubilitiesofchloroethaneandacetone.

（c）watersolubilitiesofbutaneand1-propanol.

（d）boilingpointsofacetoneand1-propanol.

Answer:

（a）Butaneisnonpolar;chloroethaneispolar.Intermolecularforcesofattractioninliquidchloroethanearelargerduetodipole-dipoleattraction;thusahigherboilingpointforchloroethane.

（b）Bothchloroethaneandacetonearepolar.However,acetoneformshydrogenbondstowatermuchmoreeffectivelythanchloroethanedoes,resultingingreatersolubilityofacetoneinwater.

（c）Butaneisnon-polarandcannotformhydrogenbonds;1-propanolispolarandcanformhydrogenbonds.1-propanolcaninteractwithwaterbybothdipole-dipoleforcesandhydrogenbonds.Butanecaninteractwithwaterbyneithermeans.Thus,1-propanolismuchmoresoluble.

（d）AcetonemoleculesareattractedtoeachotherbyvanderWaalsattractionanddipole-dipoleattraction.1-propanolmoleculesshowthesetwotypesofattraction.However,1-propanolcanalsoundergohydrogenbonding.Thisdistinguishingfeatureresultsinthehigherboilingpointof1-propanol.

1982D

（a）DrawtheLewiselectron-dotstructuresforCO32-,CO2,andCO,includingresonancestructureswhereappropriate.

（b）WhichofthethreespecieshastheshortestC-Obondlength?

Explainthereasonforyouranswer.

（c）Predictthemolecularshapesforthethreespecies.Explainhowyouarrivedatyourpredictions.

Answer:

（a）

（b）COhastheshortestbondbecausethereisatriplebond.ORbecausethereisthegreatestnumberofelectronsbetweenCandOinCO.

（c）CO32-trigonalplanar（planarandtriangular）.Cbondingissp2hybrid-or-Chasthreebondingpairsandnolonepair.

CO2linear.Cbondingissphybrid-or-Chastwobondingpairsandnolonepairs-or-CO2isnonpolarandmustbelinear.

COlinear.Twoatomsdetermineastraightline.

1982D

Thevaluesofthefirstthreeionizationenergies（I1,I2,I3）formagnesiumandargonareasfollows:

I1

I2

I3

（kJ/mol）

Mg

735

1443

7730

Ar

1525

2665

3945

（a）GivetheelectronicconfigurationsofMgandAr.

（b）Intermsoftheseconfigurations,explainwhythevaluesofthefirstandsecondionizationenergiesofMgaresignificantlylowerthanthevaluesforAr,whereasthethirdionizationenergyofMgismuchlargerthanthethirdionizationenergyofAr.

（c）IfasampleofArinonecontainerandasampleofMginanothercontainerareeachheatedandchlorineispassedintoeachcontainer,whatcompounds,ifany,willbeformed?

Explainintermsoftheelectronicconfigurationsgiveninpart（a）.

（d）ElementQhasthefollowingfirstthreeionizationenergies:

I1

I2

I3

（kJ/mol）

Q

496

4568

6920

WhatistheformulaforthemostlikelycompoundofelementQwithchlorine?

Explainthechoiceofformulaonthebasisoftheionizationenergies.

Answer:

（a）Mg:

1s22s22p63s1

Ar:

1s22s22p63s23p6

（b）ValenceelectronsforMgandArareinthesameprincipalenergylevel,butAratomissmallerandhasagreaternuclearcharge.Thus,ionizationenergiesforMgarelessthanthoseforAr.RemovalofthirdelectronfromMgatomisfromn=2levelandelectronsinthislevelexperiencestrongnuclearattraction.

（c）OnlyMgCl2forms.Mgatomsreadilylose2valenceelectronseach.Ionizationenergyforthirdelectronveryhigh.ElectronaffinityforArislow,andionizationenergiesforAratomsarehigh.

（d）FormulaisQCl.Very