《基礎(chǔ)化學(xué)》英文教學(xué)課件：chapter-6

凍筆新詩懶寫，寒爐美酒時(shí)溫。醉看墨花月白，恍疑雪滿前村。

——唐·李白《立冬》凍筆新詩懶寫，寒爐美酒時(shí)溫。Chapter6ReactionHeat,DirectionandExtentofChemicalReaction

§1.Thermodynamicsystemandstatefunction§2.Energyconservationandheatofchemicalreaction§3.EntropyandGibbsfreeenergy§4.TheextentandequilibriumconstantofchemicalreactionsChapter6ReactionHeat,§1.§1.ThermodynamicSystemandStateFunctionThermodynamics(熱力學(xué)):

isthestudyoftherelationshipbetweenheatandotherformsofenergy(includingelectricenergyandchemicalenergy,etc.)involvedinachemicalorphysicalprocess.Itisbasedonthefirstandthesecondthermodynamiclaw(empiricallaw).Chemicalthermodynamics(化學(xué)熱力學(xué)):

Heateffectofchemicalreactions,directionandextentofchemicalreactions.Itdoesnotconsiderifachemicalreactionreallyoccursornot.Itdoesnotdealwithhowachemicalreactionoccurandthereactionrate.§1.ThermodynamicSystemandSI.SystemandsurroundingsSystem(系統(tǒng)):

tobeinvestigated.Thesubstanceormixtureofsubstancesunderstudyinwhichachangeoccursiscalledthethermodynamicsystem.Surroundings(環(huán)境):

directlyrelatedtosystem.Everythinginthevicinityofthethermodynamicsystem.§1.ThermodynamicSystemandStateFunctionI.SystemandsurroundingsSystOpensystem(開放系統(tǒng)):

canexchangematteraswellasenergywithitssurroundings.Closedsystem(封閉系統(tǒng)):

canexchangeenergybutnotmatterwithitssurroundings.Isolatedsystem(孤立系統(tǒng)):

canexchangeneitherenergynormatterwithitssurroundings.§1.ThermodynamicSystemandStateFunctionOpensystem(開放系統(tǒng)):canexchanII.Process(過程)Isothermal(等溫):

Thetemperatureofthesystemremainsconstant,T=Tsurr=constant.Isobaric(等壓):

Thepressureofthesystemremainsconstant,p=psurr=constant.Isochoric(等容):

Thevolumeofthesystemremainsconstant,V=constant.Adiabatic(絕熱):

Noheatexchangewiththesurroundings,

Q=0.Cyclic(循環(huán)):

Finalstate=initialstate,U=0.§1.ThermodynamicSystemandStateFunction“Adiabatic”comesfromtheGreekwordsfor“notpassingthrough.”II.Process(過程)Isothermal(等溫III.PropertiesofasystemMacroscopicpropertiesofasystem:Pressure,volume,temperature,mass,composition,….Extensiveproperties(廣度性質(zhì)):

proportionaltothequantity(moles).Example:mass,volume.§1.ThermodynamicSystemandStateFunctionIntensiveproperties(強(qiáng)度性質(zhì)):

notdependentonthequantity(moles).Example:pressure,temperature,composition.III.PropertiesofasystemMacIV.StateandstatefunctionThestate

(狀態(tài))ofasystemisdefinedbyallpropertiesofthesystem.§1.ThermodynamicSystemandStateFunctionStateStatefunction(T,p,V,n) (U,H,S,G)Astatefunction(狀態(tài)函數(shù))isapropertyofasystem.Astatefunctiondependsonlyonitspresentstateandisindependentofanyprevioushistoryofthesystem.IV.StateandstatefunctionThStatefunction:extensiveandintensiveproperties.§1.ThermodynamicSystemandStateFunction(1)Theincrementofastatefunctionisonlydependentontheinitialandfinalstatesofthesystem,butnottheprocess.Statefunction:extensiveand373K1atm298K10atmIsobaricIsobaricIsothermalIsothermal298K1atminitialstates373K10atmfinal

states§1.ThermodynamicSystemandStateFunction373K298KIsobaricIsobaricIsot(2)Itisnotnecessarytolistoutallpropertiestodescribeastateofasystem.Forexample,thestateequationofidealgas:pV=nRT.p,V,Tn§1.ThermodynamicSystemandStateFunction(2)Itisnotnecessarytolis§1.ThermodynamicSystemandStateFunctionV.Internalenergy(內(nèi)能)Energy:canbebrieflydefinedasthepotentialorcapacitytomovematter.Kineticenergy(動(dòng)能):

theenergyassociatedwithanobjectbyvirtueofitsmotion.1.EnergyEnergycanexistindifferentforms,includingheat,light,electrical,andchemicalenergy,andthesedifferentformscanbeinterconverted.§1.ThermodynamicSystemandS§1.ThermodynamicSystemandStateFunctionTheSIunitofenergy,kg·m2·s-2,isgiventhenamejoule(焦耳,J).Thecalorie(卡路里,cal)isanon-SIunitofenergycommonlyused,originallydefinedastheamountofenergyrequiredtoraisethetemperatureofonegramofwaterbyonedegreeCelsius.(exactdefinition)§1.ThermodynamicSystemandS《基礎(chǔ)化學(xué)》英文教學(xué)課件：chapter_69Calorie/1g4Calorie/1gCalorie(大卡)=1kilocalorie(千卡)=1000calorie(卡)

=4.184kJ9Calorie/1g4Calorie/1gCa§1.ThermodynamicSystemandStateFunctionPotentialenergy(勢(shì)能):

theenergyanobjecthasbyvirtueofitspositioninafieldofforce.§1.ThermodynamicSystemandS§1.ThermodynamicSystemandStateFunctionInternalenergy(內(nèi)能,U):Thesumofthekineticandpotentialenergiesoftheparticlesmakingupasystemisreferredtoastheinternalenergy.2.Internalenergy(U)ThewaterasawholehasEkandEp.However,H2Omoleculesaremadeupofsmallerparticles,electronsandnuclei.Eachoftheseparticlesalsohaskineticandpotentialenergy.U:extensiveproperty;absolutevalueofU?U:statefunction,U=(Ufinal-Uinitial)§1.ThermodynamicSystemandS§1.ThermodynamicSystemandStateFunctionThetotalenergyofaquantityofasubstanceequalsthesumofitskineticandpotentialenergiesasawholeplusitsinternalenergy.Normallywhenyoustudyasubstanceinthelab,thesubstanceisatrestinavessel.ItsEkasawholeiszero.Moreover,itsEpasawholeisconstantandcanbetakentobezero.Inthiscase,thetotalenergyofthesubstanceequalsitsinternalenergy,U.§1.ThermodynamicSystemandSVI.Heat(Q)andwork(W)Twoformsofenergyexchangebetweenasystemanditssurroundings.§1.ThermodynamicSystemandStateFunctionHeatflowsfromaregionofhighertemperaturetooneoflowertemperature;oncethetemperaturebecomeequal(thermalequilibrium),heatflowstops.Youwouldnotsaythatthesystemhasheat,becauseheatisonlyanenergyflow.Heat(熱,Q)

isdefinedastheenergythatflowsintooroutofasystembecauseofadifferenceintemperaturebetweenthesystemanditssurroundings.

VI.Heat(Q)andwork(W)TwofWork(功,W)

istheenergyexchangethatresultswhenaforceFmovesanobjectthroughadistanced;workequalsW=F×d.§1.ThermodynamicSystemandStateFunctionHeatisabsorbedbythesystem:

(endothermic,吸熱):Q>0;Heatisreleasedbythesystem:

(exothermic,放熱):Q<0.Volumework(We);Electricwork,surfacework,….(Wf)Workdoneonthesystem:W>0;Workdonebythesystem:W<0Work(功,W)istheenergyexchaHeatandworkarenotstatefunctions,theyaredependentonthespecificprocess.§1.ThermodynamicSystemandStateFunctionHeatandworkarenotstatefuTTApoutlIsothermalexpansionofidealgas(理想氣體的等溫膨脹)

(pV=nRT)pinitial=405.2kPa,Vinitial=1.00L,Tinitial=273KInitialstate:pfinal=101.3kPa,Vfinal=4.00L,Tfinal=273KFinalstate:Example:§1.ThermodynamicSystemandStateFunctionTTApoutlIsothermalexpansionoTTApoutlIsothermalexpansionofidealgaspinitial=405.2kPaVinitial=1.00LTinitial=273Kpfinal=101.3kPaVfinal=4.00LTfinal=273Kpout=101.3kPa(1)p2=202.6kPaV2=2.00LTfinal=273K(2)pout=202.6kPa(I)pout=101.3kPa(II)Reversibleprocess(可逆過程)(3)§1.ThermodynamicSystemandStateFunctionTTApoutlIsothermalexpansiono(1) (2) TTApoutl§1.ThermodynamicSystemandStateFunction(1) (2) TTApoutl§1.ThermodynaW3>W2>W1§1.ThermodynamicSystemandStateFunctionHeatandworkarenotstatefunctions,theyaredependentonthespecificprocess.W3>W2>W1§1.ThermodyIsothermalexpansionofidealgasp1,V1p2,V2pVp1,V1p2,V2pVp1,V1p2,V2pV(1)(2)(3)Process(3)isareversible(可逆的)process.W3=Wmax

§1.ThermodynamicSystemandStateFunctionIsothermalexpansionofideal

§2.ConservationofEnergy&HeatofReactionI.Thefirstlawofthermodynamics(熱力學(xué)第一定律)Thefirstlawofthermodynamicsstatesthattheinternalenergyofanisolatedsystemisconstant.Foraclosedsystem,themathematicalexpressionofthefirstlawofthermodynamics:

U=Q+WLater,W=We,Wf=0.Energycanneverbecreatedordestroyedinordinarychemicalreactionsandphysicalchanges,itcanonlytransformfromoneformtoanother.§2.ConservationofEnergy&

§2.ConservationofEnergy&HeatofReactionThissystemgainsinternalenergyfromtheheatabsorbed(165J)andlosesinternalenergyviatheworkdone(92J).Thusthenetchangeofinternalenergyis:§2.ConservationofEnergy&FritzHaber(1868-1934)NobelPrizeChemistry(1918)HaberProcess（哈伯循環(huán)）§2.ConservationofEnergy&HeatofReactionFritzHaberNobelPrizeChemist

§2.ConservationofEnergy&HeatofReactionII.Heatofreaction(反應(yīng)熱)Twocrystallinesubstances,Ba(OH)2·8H2OandNH4NO3,aremixedthoroughlyinaflask.Thentheflask,whichfeelsquitecoldtothetouch,issetinapuddleofwateronaboard.Inacoupleofminutes,theflaskandboardarefrozensolidlytogether.Theboardcanthenbeinvertedwiththeflaskfrozentoit.§2.ConservationofEnergy&

§2.ConservationofEnergy&HeatofReactionTheheatofreaction(atagiventemperature)isthevalueofQrequiredtoreturnasystemtothegiventemperatureatthecompletionofthereaction.(endothermic)1molBa(OH)2,(exothermic)1molCH4,§2.ConservationofEnergy&

§2.ConservationofEnergy&HeatofReactionMeasurementofheatofreaction(heretheheatofcombustionofgraphite).Bombcalorimeter(彈式量熱計(jì)):adeviceusedtomeasuretheheatabsorbedorreleasedduringaphysicalorchemicalchange.§2.ConservationofEnergy&Biocalorimetry(生物量熱學(xué))微量量熱技術(shù)

10203040t/h（1）ADSⅠE用肉胨培養(yǎng)的細(xì)菌特征熱譜圖（2）ADSⅡF用肉胨培養(yǎng)細(xì)菌26h后加抗生素的細(xì)菌特征熱譜圖§2.ConservationofEnergy&HeatofReactionBiocalorimetry(生物量熱學(xué))10III.Isochoricreactionheat(等容反應(yīng)熱)U=QV+W =QV+pV =QVConsiderachemicalreactionunderanisochoricconditions(Q=QV,V=0):U=QVTheheatofreactionatconstantvolume(isochoricreactionheat)equalsthechangeininternalenergyforthereaction.§2.ConservationofEnergy&HeatofReactionIII.Isochoricreactionheat(IV.Enthalpy(焓)andisobaricreactionheat(等壓反應(yīng)熱)U=Ufinal–Uinitial=Qp+WConsiderachemicalreactionunderanisobaricconditions(Q=Qp):Forisobaricprocess:pinitial=pfinal=pout,then:(Ufinal+pfinalVfinal)–(Uinitial+pinitialVinitial)=QpHU+pV(definition)§2.ConservationofEnergy&HeatofReactionW=-poutV=-pout(Vfinal–Vinitial)IV.Enthalpy(焓)andisobaricrH=QpHfinal–Hinitial=Qp§2.ConservationofEnergy&HeatofReactionH:

enthalpy(焓),statefunction,extensiveproperties.Theheatofreactionatconstantpressure(isobaricreactionheat)equalsthechangeinenthalpyforthereaction.HU+pVH=QpHfinal–Hinitial=Qp§U=QVU=Q+WQV=Qp+WQV=Qp-PV(s.l,⊿n=0)QV=QpQV=Qp-PV(g)Qp=QV+nRTn=∑n(products)-∑n(reactants)§2.ConservationofEnergy&HeatofReactionU=QVU=Q+WQV=Qp+WQVExample:298K，1atm，2molH2and1molO2weremixed,and2molH2O(l)wasproducedafteracertaintime.Calculatetheextentofreactionofisochoricreactionheatandisobaricreactionheat,1molH2O(l)wasproduced

.2H2(g)+O2(g)=2H2O(l)Q=-571.6kJ·mol-1Solution:Qp=-285.8kJ·mol-11molH2O(l)wasproducedn=∑n(products)-∑n(reactants)=-3nRT=-7433J=-7.4kJQp=QV+nRT§2.ConservationofEnergy&HeatofReactionExample:298K，1atm，2molH2aQp=QV+nRTQV=Qp-nRT=-282.1

kJ·mol-1QV≈Qp1molH2O(l):nRT=-3.7kJ·mol-1Qp=-285.8kJ·mol-1H=QpU=QVH≈UQp=QV+nRTQV=Qp-nRT=§2.ConservationofEnergy&HeatofReactionThechangeinenthalpyforareactionatagiventemperatureandpressure(H,alsocalledtheenthalpyofreaction,反應(yīng)焓)isobtainedbysubtractingtheenthalpyofthereactants(initialstate)fromtheenthalpyoftheproducts(finalstate).§2.ConservationofEnergy&HV.Extentofreaction(反應(yīng)進(jìn)度)Forareaction:B:reactantsorproducts;B:stoichiometriccoefficientofB;B(product)>0;B(reactant)<0.Extentofreactionξ(ksai):§2.ConservationofEnergy&HeatofReactionV.Extentofreaction(反應(yīng)進(jìn)度)FoExample6-1:10.0molH2and5.0molN2weremixed,and2.0molNH3wasproducedafteracertaintime.Calculatetheextentofreactionof(1)and(2).(1) (2)Solution:Accordingtoreaction(1):§2.ConservationofEnergy&HeatofReactionToproduce2.0molofNH3,1molofN2and3molofH2wereconsumed,respectively.Example6-1:10.0molH2and5Accordingtoreaction(2):§2.ConservationofEnergy&HeatofReactionExtentofreactionremainsthesamenomatterwhichreactantsorwhichproductsareusedtocalculateit.Extentofreactionisafunctionofstoichiometriccoefficientofreactantsandproducts.Accordingtoreaction(2):§2.VI.Thermochemicalequations(熱化學(xué)方程)§2.ConservationofEnergy&HeatofReactionH:isobaricreactionheat(enthalpyofreaction);Definition:thechemicalequationforareaction(includingphaselabels)inwhichtheenthalpyofreaction(H)iswrittendirectlyaftertheequation.“r”:reaction;“m”:=1mol;:standardstate.VI.Thermochemicalequations(§2.ConservationofEnergy&HeatofReactionThetemperatureis298.15K(25oC)ifotherwisestated.PureGas&PureLiquid:p=100kPa(1bar).Standardstate(標(biāo)準(zhǔn)態(tài)):Thestandardthermodynamicconditionschosenforsubstanceswhenlistingorcomparingthermodynamicdata:

standardpressurep(100kPa,1bar)andthe(any)specifiedtemperature(usually25oC).Solute(insolution):p=100kPa,c=1mol·L-1.§2.ConservationofEnergy&H§2.ConservationofEnergy&HeatofReactionThestandardstateusedtobedefinedfor1atmratherthanfor1bar;however,thelatterisnowtheacceptedstandard.Thesmallchangeinstandardpressuremakesanegligibledifferencetomostnumericalvalues,soitisnormallysafetousetablesofdatacompiledfor1atm.Thisequationsaysthat,at25oC,1molofhydrogengas(partialpressureof100kPa)reactswithone-halfmolofoxygengas(partialpressureof1bar)toproduce1molofliquidwater(partialpressureof1bar),and285.83kJofheatisreleased.§2.ConservationofEnergy&H§2.ConservationofEnergy&HeatofReaction①H2(g)+1/2O2(g)=H2O(l)Notes:1.Whenathermochemicalequationismultipliedbyanyfactor,thevalueofHforthenewequationisobtainedbymultiplyingthevalueofHintheoriginalequationbythesamefactor.2.Whenachemicalequationisreversed,thevalueofHisreversedinsign.③H2O(l)=1/2O2(g)+H2(g)②2H2(g)+O2(g)=2H2O(l)①H2(g)+1/2O2(g)=H2O(l)§2.ConservationofEnergy&H§2.ConservationofEnergy&HeatofReactionVII.Fuels(燃料)Afuelisanysubstancethatisburnedorsimilarlyreactedtoprovideheatandotherformsofenergy.Thehumanbodyrequiresaboutasmuchasenergyinadayasdoesa100-wattlightbulb.1.Foodsasfuels.Carbohydrate:Fat:§2.ConservationofEnergy&H§2.ConservationofEnergy&HeatofReactionPetroleumsupplieswillbe80%depletedatabouttheyear2030.Natural-gassuppliesmaybedepletedevensooner.Coalsuppliesaresufficienttolastseveralcenturies.Thisabundancehasspurredmuchresearchintodevelopingcommercialmethodsforconvertingcoaltomoreeasilyhandledliquidandgaseousfuels.2.Fossilfuels.SolidCoal(煤):Liquidpetroleum(石油):Naturalgas(天然氣):§2.ConservationofEnergy&H§2.ConservationofEnergy&HeatofReaction3.Rocketfuels.ThefirststageoftheSaturnVlaunchvehicle(thatsentathree-manApollocrewtothemoon)used:Anunbelievable550tonsofkerosenewereburnedin2.5minutes(1.62×1011watts).Thesecondandthirdstageofliftoffusedliquidhydrogen(b.p.–253C)/oxygen(b.p.–183C)system:§2.ConservationofEnergy&H§2.ConservationofEnergy&HeatofReactionThelandingmodulefortheApollomissionusedafuelofhydrazineandanoxidizerofdinitrogentetroxide:Solidfuels(containingaluminummetalpowderand

othermaterialswithammoniumperchlorate

astheoxidizer)wereusedintheboosterrocketsoftheColumbiaspaceshuttle.Acloudofaluminumoxideformsastherocketsburn.§2.ConservationofEnergy&HVIII.Hess’slawHess’slawstatesthatforachemicalequationthatcanbewrittenasthesumoftwoormoresteps,theenthalpychangefortheoverallequationequalsthesumofenthalpychangesfortheindividualsteps.§2.ConservationofEnergy&HeatofReactionNomatterhowyougofromgivenreactantstoproducts,theenthalpychangefortheoverallchemicalchangeisthesame.reactantsproductsVIII.Hess’slawHess’slawsta§2.ConservationofEnergy&HeatofReaction§2.ConservationofEnergy&HⅨ.Calculatingtheisobaricreactionheat(enthalpyofreaction)1.Fromknownthermochemicalequations:Example6-2:(1)C(gra)+O2(g)=CO2(g)(2)CO(g)+?O2(g)=CO2(g)Calculatetheenthalpyofthefollowingreaction: (3)C(gra)+?O2(g)=CO(g).§2.ConservationofEnergy&HeatofReactionⅨ.CalculatingtheisobaricreSolution:§2.ConservationofEnergy&HeatofReactionC(gra)+O2(g)=CO2(g)CO(g)+?O2(g)=CO2(g)C(gra)+?O2(g)=CO(g)––Solution:§2.ConservationofEThermochemicalequationsfortheindividualstepsofareactionsequencemaybecombinedtogivethethermochemicalequationsfortheoverallreaction.§2.ConservationofEnergy&HeatofReactionC(gra)+O2(g)=CO2(g)CO(g)+?O2(g)=CO2(g)C(gra)+?O2(g)-CO(g)=0–C(gra)+?O2(g)=CO(g)CO(g)=C(gra)+?O2(g)Thermochemicalequationsfort2.FromstandardmolarenthalpiesofformationStandardmolarenthalpyofformation(標(biāo)準(zhǔn)摩爾生成焓)ofasubstance

istheenthalpychangefortheformationofonemoleofthesubstanceinitsstandardstatefromitselementsintheirmoststableformandintheirstandardstates.§2.ConservationofEnergy&HeatofReaction2.Fromstandardmolarenthalp§2.ConservationofEnergy&HeatofReactionAlthoughthereferenceformisusuallythestablestformofanelement,thechoiceisessentiallyarbitraryaslongasoneisconsistent.§2.ConservationofEnergy&HAllotropesofsulfurLeft:rhombicsulfur,thestableformoftheelementatroomtemperature.Right:Whenthissulfurismelted,thencooled,itformslongneedlesofmonoclinicsulfur,anotherallotrope.Atroomtemperature,monoclinicsulfurwillslowlychangebacktorhombicsulfur.Allotropesofsulfur《基礎(chǔ)化學(xué)》英文教學(xué)課件：chapter_6elementsproductsreactants§2.ConservationofEnergy&HeatofReactionStandardmolarenthalpiesofformationcanbecombinedtoobtainthestandardenthalpyofanyreaction.isthemathematicalsymbolmeaning“thesumof”,andmandnarethecoefficientsofthesubstancesinthechemicalequation.elementsproductsreactants§2.C§2.ConservationofEnergy&HeatofReaction§2.ConservationofEnergy&H2NH3(g)+CO2(g)=CO(NH2)2(s)+H2O(l)Solution:Example6-3:Calculatethestandardreactionenthalpyofthefollowingreactionat298.15Kaccordingtodata.§2.ConservationofEnergy&HeatofReaction2NH3(g)+CO2(g)=CO(NH2)2(sWhatistheenthalpyofreaction,H,fortheformationoftungstencarbide,WC,fromtheelements?(Tungstencarbideisveryhardandisusedtomakecuttingtoolsandrockdrills.)Theenthalpychangeforthisreactionisdifficulttomeasuredirectly,becausethereactionoccursat1400oC.However,theheatsofcombustionoftheelementsandoftungstencarbidecanbemeasuredeasily:Exercise:Whatistheenthalpyofreacti§2.ConservationofEnergy&HeatofReactionrHmisessentiallyconstantwithrespecttotemperature.Thisapproximationismostaccuratefortemperaturenottoodifferentfromthetemperature(25oC)forwhichtherHmisobtained.Muchdifferenttemperaturesgivegreatererror.?§2.ConservationofEnergy&H3.FromstandardmolarenthalpiesofcombustionStandardmolarenthalpyofcombustion(標(biāo)準(zhǔn)摩爾燃燒焓)ofasubstanceistheenthalpychangeforthecompletecombustion(oxidation)ofonemoleofthesubstanceinitsstandardstatetoproductsintheirmoststableformandintheirstandardstates.§2.ConservationofEnergy&HeatofReaction3.FromstandardmolarenthalpreactantscombustionproductsproductsStandardmolarenthalpiesofcombustioncanbecombinedtoobtainthestandardenthalpyofanyreaction.§2.ConservationofEnergy&HeatofReactionreactantscombustionproductsprExample6-4:Calculatethestandardreactionenthalpyofthefollowingreactionat298.15Kaccordingtothestandardmolarenthalpyofcombustiondata.CH3CHO(l)+H2(g)=C2H5OH(l)Solution:§2.ConservationofEnergy&HeatofReactionExample6-4:Calculatethesta§3.EntropyandGibbsFreeEnergyI.Spontaneousprocess(自發(fā)過程)Somethingshappennaturally;somethingsdon’t.Waterflowsdownhillnaturally;wehavetopumpituphill.Heatflowsfromanhotobjecttoacoldone;arefrigeratorisneededtomakeheatflowfromacoldtoahotobject.Anironrustsinmoistair;butitrequireschemicalreactionstoconvertrusttoiron.§3.EntropyandGibbsFreeEne§3.EntropyandGibbsFreeEnergyI.Spontaneousprocess(自發(fā)過程)Aspontaneousprocessisaprocessthathasanaturaltendencytooccurwithoutbeingdrivenbyanexternalinfluence.Itisimportanttoappreciatethataspontaneouschangeneednotnecessarilytakeplaceatasignificantrate.Diamondshaveanaturaltendencytoturnintographite,butdiamondslastunchangedforcountlessyears----diamondsare,forpractice,forever.§3.EntropyandGibbsFreeEneKULeuvenAfdelingFotochemieenSpectroscopieProf.Dr.F.C.DeSchryverKULeuven71§3.EntropyandGibbsFreeEnergy(endothermic)Spontaneousreactionsmustbeexothermic(H<0)?§3.EntropyandGibbsFreeEneKULeuvenAfdelingFotochemieenSpectroscopieProf.Dr.F.C.DeSchryverKULeuven73II.Disorder(混亂度)andentropy(熵)Asingleideaaccountsforallspontaneouschange:Energyandmattertendtobecomemoredisordered.§3.EntropyandGibbsFreeEnergyEntropy,S,isathermodynamicquantitythatisameasureoftherandomnessordisorderinasystem.SIunit:J·K-1.Entropy:

statefunction:Itsquantityinagivenamountofsubstancedependsonlyonvariables(e.g,TandP)thatdeterminesthestateofthesubstance.1.EntropyII.Disorder(混亂度)andentropy§3.EntropyandGibbsFreeEnergy1moloficeat0oCand100kPahasanentropyof41J·K-1.1molofliquidwaterat0oCand100kPahasanentropyof63J·K-1.Forthemeltingoficetoliquidwater,Theentropyincreasesbecauseasubstancebecomesmoredisorderedwhenitmelts.§3.EntropyandGibbsFreeEne§3.EntropyandGibbsFreeEnergy2.Entropychangeforisothermalprocessesr:reversible.Whenasystemisatequilibrium,asmallchangeinaconditioncanmaketheprocessgoinonedirectionortheother.(熱溫商)§3.EntropyandGibbsFreeEneThethirdlawofthermodynamics:Asubstancethatisperfectlycrystallineat0Khasanentropyofzero.§3.EntropyandGibbsFreeEnergy3.ThethirdlawofthermodynamicsThethirdlawisthekeytoestimatetheentropy(conventionalentropy,規(guī)定熵)ofasubstanceatanytemperature,S(T),becauseittellsthatS(0)=0.Thethirdlawofthermodynamic§3.EntropyandGibbsFreeEnergy§3.EntropyandGibbsFreeEne§3.EntropyandGibbsFreeEnergy(1):Thestandardmolarentropyofagasishigherthanthatofthecorrespondingsolidandliquidatthesametemperature.(2):Standardmolarentropiesincreaseasthecomplexityofsubstancesincreases.Standardmolarentropy(標(biāo)準(zhǔn)摩爾熵),:Theconventionalentropyof1moleofsubstanceunderstandardstate(100kPa).Unit:J·K-1·mol-1.Homologousseries(同系物)§3.EntropyandGibbsFreeEne(3):Standardmolarentropiesincreasewiththetemperature.§3.EntropyandGibbsFreeEnergy(3):Standardmolarentropies§3.EntropyandGibbsFreeEnergyStandardmolarentropychangeforareaction(rSm):isthedifferenceinstandardmolarentropiesoftheproductsandreactants,takingintoaccounttheirstoichiometriccoefficients.Example6-5:Calculatethestandardmolarentropychange,rSm,at25oCforthereactioninwhichureaisformedfromNH3andCO2.§3.EntropyandGibbsFreeEne§3.EntropyandGibbsFreeEnergySolution:2NH3(g)+CO2(g)NH2CONH2(aq)+H2O(l)§3.EntropyandGibbsFreeEne§3.EntropyandGibbsFreeEnergyTheentropyusuallyincreasesinthefollowingsituations:TopredicttheentropychangeforareactionAreactioninwhichamoleculeisbrokenintotwoormoresmallermolecules.Areactioninwhichthereisanincreaseinmolesofgas.Aprocessinwhichasolidchangestoliquidorgasoraliquidchangestoagas.§3.EntropyandGibbsFreeEne§3.EntropyandGibbsFreeEnergyExample6-6:Predictthesignoftheentropychangeofthefollowingreaction:Solution:Amoleculebreaksintosmallermolecules.Moreover,thisresultsinagasbeingreleased.Youpredictthattheentropyincreases.Inthisreaction,themolesofgasdecrease,whichwoulddecreasetheentropy.Youpredictthattheentropyshoulddecrease.Becausethereisnochangeinthenumberofmolesofgas,youcannotpredictthesignofentropychange.§3.EntropyandGibbsFreeEneIII.ThesecondlawofthermodynamicsTheentropyofanisolatedsystemincreaseinthecourseofanyspontaneousprocess.Theactualsystemanditssurro