KineticMolecularTheory,Gases,andPhaseChanges(AnswerKey)

8.Seeabove.

9.Endothermic:melting,evaporation,sublimation.Exothermic:freezing,condensation,deposition.

Meltingisendothermicbecauseenergyisabsorbedbythesolidinordertobreakintermolecularforces(IMFs)andbecomealiquid.Freezingisexothermicbecausetheparticlesoftheliquidlosekineticenergy,slowdown,andformintermolecularforcestobecomeasolid.

10. AtoB:Solidisheatingup(increasingtemperature)asenergyisadded

BtoC:Solidintermolecularforces(IMFs)arebreakingasenergyisadded,temperatureisNOTincreasing.

CtoD:Liquidisheatingup(increasingtemperature)asenergyisadded

DtoE:LiquidIMFsarebreakingasenergyisadded,temperatureisNOTincreasing.

EtoF:Gasisheatingup(increasingtemperature)asenergyisadded

11.Addingenergycausesthekineticenergyofparticlestoincrease,increasingtemperatureandbreakingintermolecularforcesandcausingaphasechange.Removingenergyallowsparticlestoslowandformnewintermolecularforces,alsocausingphasechanges.

12.Intermolecularforcesaretheforcesofattractionbetweenparticlesholdingthemtogether.SolidshavestrongIMFs,liquidshavemediumIMFs,andgaseshaveweakornoIMFsatall.

13.Conductionisthetransferofheatthroughamaterial.Whenheatisappliedtoonelocation,theparticlestheregainkineticenergyandmovemorerapidly.Theycollidewiththeirneighbors,givingthemincreasedkineticenergy,andthoseneighborscollidewiththeirneighbors,andsoonthroughoutthematerial.Conductionhappensmuchmorequicklyinsolidsbecausetheparticlesarealwayssidebysideandcollidemuchmoreoftenandeasily.Inagas,particlesaresofarapartthattheyalmostnevercollide,sotheaddedkineticenergyisnottransferred.

14.Asolidconsistsofparticlesinarigidarrangement,permanentlyheldnexttotheirneighborsbyintermolecularforces.Theseparticlesareconstantlyvibratinginplace.Aliquidconsistsofparticlesstillclosetogether,butabletoflowpastandaroundeachother.Agasconsistsofparticlesfarapartfromeachother,movingfreelyandrarelycolliding.

liquidsolid

gas

melting

freezingevaporation

condensation

sublimation

deposition

15.a)Astemperatureofagasincreases,pressureincreases.(directrelationship)(GayLussacLaw)*Volumeisconstant

b)Astemperatureofagasincreases,volumeincreases.(directrelationship)(CharlesLaw)*Pressureisconstant

c)Asthevolumeofagasincreases,thepressuredecreases.(inverserelationship)(Boyle’sLaw)*Temperatureisconstant

Graphs:

16.Increasingkineticenergycausestemperaturetoincrease,whichalsocausesvolumeandpressuretoincrease.

17.TheparticlesoftheicecubehavelowkineticenergyandareheldtogetherbystrongIMFsbecausetheyareinthesolidstate.Theparticlesofthesodaarewarmerandmovingaroundwithgreaterkineticenergybecausetheyareintheliquidstate.Theparticlesofthesodacollidewiththeparticlesoftheicecube.Thiscausessomeoftheintermolecularforcestobreakandtheicecubeparticlesgainkineticenergy,eventuallybreakingfreefromtheicecubeandbecomingliquid.Thesodaparticlesloseenergyinthecollisions,sothedrinkgetscolder.

Acid,BaseChemistry(answerkey)

18.Seeabove.

19.Limestone(calciumcarbonate)isaweakbasethatkeepslakewateratapHof8-9.Whenacidrainfallsintheselakes,thebaseneutralizestheacidrain,maintainingapHnear7,sothelakedoesnotgettooacidic.Lakeswithgraniterocksdonothavetheprotectivebaseproperties,sotheacidraincausesthepHofthelakewatertofall,harminganimalsandplants.

20.Redlitmuspaperturnsblueinabase;bluelitmuspaperturnsredinanacid.

21.HydroniumisH3O+.ItisformedwhenanacidreleasesH+whichcombineswithH2O

Strongacid

Weakacid

Neutral Weakbase

Strongbase

22.AtapHof0,hydronium/hydrogenion(H3O+)concentrationisveryhighandthesolutionisveryacidic,andthereiszerohydroxide(OH-).AtapHof14,theconcentrationofOH-isveryhigh,whiletheconcentrationofH3O+iszero.AtaneutralpHof7,theconcentrationofOH-andH3O+isexactlyequal.

23.

• Arrheniusacid:producesH+.• Arrheniusbase:producesOH-.• Brønsted-Lowryacid:donatesH+.• Brønsted-Lowrybase:acceptsH+

24.Generally,acompoundstartingwithHisanacid.CompoundscontainingOHarebases.NH3(ammonia)isanothercommonbase.

• HClacid(hydrochloricacid)• NaOHbase(sodiumhydroxide)• KOHbase(potassiumhydroxide)• HBracid(hydrobromicacid)• NH3base(ammonia)(acceptsprotontobecomeNH4+)• HNO3acid(nitricacid)• Mg(OH)2base(magnesiumhydroxide)• HFacid(hydrofluoricacid)• H2SO4acid(sulfuricacid)

25.AneutralizationreactionalwaysproducesWATERandSALT(ioniccompound).Thegeneralequationis:Acid+baseàwater+salt

26.

a) 2KOH + H2CO3 � 2H2O + K2CO3

(NOTE:CO32-hasa2-charge,whileK+hasa1+charge,sotwoK+ionsareneededtobalance)

b) HF + LiOH � H2O + LiF

OrganicChemistry(Answerkey)

27.Anorganiccompoundcontainscarbon.(Specifically,carbonbondedtohydrogen)

28.Carboncanform4bondsbecauseithas4valenceelectrons,soithas4“emptyslots”toformbonds.

29. EthaneC2H6 PentaneC5H12

Propane:C3H8

NAMINGTIP:Hydrocarbons(chainsofhydrogenandcarbon)arenamedbytheirnumberof

carbonsstartingat5.PENTANE=5,HEXANE=6,HEPTANE=7,OCTANE=8.

30.C6H14ishexane–itsstructuralisomersincludeanyarrangementofcarbonsinsinglebondedchains,straightorbranched.Therearefivepossibilities.Itishelpfultodrawthemsimplyaslines,whereeachcornerisacarbon.Twodifferentwaysofdrawingthemareshownbelow.