结构物化厦大chapter12

1Chapter12ponentPhaseEquilibriumPhysicalChemistryponentPhase2QuestionandAnswering

PhysicalChemistryAStudent’sQuestion我昨天晚上看了第9章的38题，想到了一个问题，在2种组分的理想混合溶液中，一种组分所占整个体系的摩尔分数与它的蒸汽所占整个体系气体的摩尔分数和它的液态部分所占整个体系液态部分的摩尔分数之间有什么关系？也就是与和三者有什么关系？是不是？但仔细想又不对！

Question:3QuestionandAnswering

PhysicalChemistryAStudent’sQuestionRaoult’sLaw:Answers.Dalton’sLaw:ABCase(1)Case(2)Case(3)4ColligativeProperties

Colligativepropertiesstemfromthereductionofthechemicalpotentialoftheliquidsolventasaresultofthepresenceofsolute.ColligativePropertiesVapor-pressureloweringFreezing-pointdepressionBoiling-pointelevationOsmoticpressureThesoluteisnotvolatileThesolutedoesnotdissolveinthesolidsolventPhysicalChemistryponentPhase5ColligativeProperties

Vapor-pressureloweringPA/torrx(sucrose)0-400.1Fig.12.1nonvolatilesolute(12.1)nonvolatilesolute(12.2)(Nocontributiontothevapor)Ifthesolutionisverydilute,ideallydilutesolution,nonvolatilesolute(12.3)ideallydilutesolutionPhysicalChemistryponentPhase6ColligativeProperties

Freezing-pointdepression(12.13)ideallydil.soln.,pureAfreezesoutmolarfreezing-point-depressionconstant

ATFig.12.2A(s)A(l)A(sln)Freezing-pointdepression(12.15)*(12.16)PhysicalChemistryponentPhase7ColligativeProperties

Boiling-pointelevationideallydil.soln.,nonvol.solutemolarboiling-point-elevationconstant(12.18)*(12.19)

ATA(l)A(s)A(v)Boiling-pointelevationPhysicalChemistryponentPhase8ColligativeProperties

Thevaporpressureofapureliquidrepresentsabalancebetweentheincreaseddisorderarisingfromvaporizationandthedecreaseddisorderofthesurroundings.

Whensoluteispresent,thedisorderofthecondensedphaseisrelativelyhigherthanthatofthepureliquid,andthereisadecreasedtendencytoacquirethedisordercharacteristicofthevapor.PhysicalChemistryponentPhase9ColligativeProperties

Equilib.atTforvaporandliquidphasesofthesolventrearrangesto(AssumingTindependent)WhenxB=0,theboilingpointisandPhysicalChemistryponentPhase10ColligativeProperties

SupposethattheamountofsolutepresentissosmallthatthenPhysicalChemistryponentPhase11ColligativeProperties

sinceitalsofollowsthat(P344)ForverydilutesolutionPhysicalChemistryponentPhase12ColligativeProperties

Osmoticpressure(12.20)(12.26)EqualatequilibriumPureASolutionofB+ASemipermeablemembrane(A)ideallydil.soln.(12.27)*van’tHoff’slaw,validinthelimitofinfinitedilutionPhysicalChemistryponentPhase13ColligativeProperties

OsmoticpressureTheosmoticpressureinanonideallydilutenonelectrolyteponentsolution(12.28)(8.4)Inthelimitofinfinitesolutionvan’tHofflawPhysicalChemistryponentPhase14f=2－φ＋2＝4－φ，φ＝1， f＝3φ＝2， f＝2φ＝3， f＝1φ＝4， f＝0 ponentphasediagramsIfonephase,thenthreefreedoms:TPxInsteadofplottingcompletephasediagrams(threedimensional),usuallyconsideronlyportionofthephasediagramatatime.PhysicalChemistryponentPhase15ponentphasediagramsKeeponeconstant,getrelationsfortwovariablesKeepTconstant,getP-x(verycommonlyused)KeepPconstant,getT-x(commonlyused)Keepxconstant,getT-P(notverycommonlyused)PhysicalChemistryponentPhase16l(A+B)C6H5CH3(A)C6H6(B)yB0.00.20.40.60.81.00.80.60.20.40.00.00.20.40.60.81.0v(A+B)T=79.7

℃yG,B=0.60HFxBl(A+B)Il(A+B)v(A+B)P/102kPatielineADEisoplethlineH,IendpointIdealsolutionatfixedTPhysicalChemistryponentPhase17l(A+B)010.80.60.20.40.00.00.20.40.60.81.0v(A+B)T=79.7

℃HFxBl(A+B)Il(A+B)v(A+B)P/102kPaADEponentphasediagrams(12.40)(12.39)LeverrulePhysicalChemistryponentPhase180.01.0l(A+B)C6H5CH3(A)C6H6(B)xByB12010060800.00.00.20.40.60.81.0t/℃v(A+B)P=101325PaliquidSQRLNTemperaturevscompositionliquid-vaporphasediagram(C6H5CH3(A)-C6H6(B))l+vIdealsolutionatfixedPvaporBoiling-pointcurvePSuccessiveboilingsandcondensationsofaliquidoriginallyofcompositiona1leadtoacondensatethatispureBa1FractionaldistillationPhysicalChemistryponentPhase19ponentphasediagramsNonidealSolutionAlow-boilingazeotropeAhigh-boilingazeotropeminimum-boilingazeotropemaximum-boilingazeotropelVapor

l+vVapor

Liquid

l+vl+vl+vAzeotropes

PhysicalChemistryponentPhase20ponentphasediagramsAmaximuminthephasediagrammayoccurwhenthefavorableinteractionsbetweenAandBmoleculesreducethevaporpressureofthemixturebelowtheidealvaluePhasediagramshowingaminimumPhasediagramshowingamaximumThemixture:formanazeotropeWhentheazeotropiccompositionhasbeenreached,distillationcannotseparatethetwoliquidsbecausethecondensatehasthesamecompositionastheazeotropicliquid.PhysicalChemistryponentPhase21ponentphasediagramsExamplesofazeotropeformation:Hydrochloricacid/waterat80%bymassofwaterandboilsunchangedat108.6oC.Ethanol/waterat4%bymassofwaterandboilsunchangedat78.0oC.Ahigh-boilingazeotrope.Alow-boilingazeotrope.PhysicalChemistryponentPhase22ponentphasediagramsLiquid-liquidequilibriumTwopartiallymiscibleliquids0.00.20.40.60.81.0l(A+B)H2O(A)C6H5NH2(B)xBt/℃1601204080P=const.T