物理化学英文2The-First-Law课件

PhysicalChemistryTheFirstLawPhysicalChemistryTheFirstLawTheConceptsTheFirstLawTheConceptsSystemandSurroundingsSystem-thepartoftheworldinwhichwehaveaspecialinterest.

Surroundings-wherewemakeourobservations.systemsurroundingsSystemandSurroundingsSystemTypesofSystemsOpen-exchangesmatterandenergywithsurroundings.

Closed-exchangesonlyenergywithsurroundings.

Isolated-nointerchangewithsurroundings.EnergyEnergyMatterTypesofSystemsOpen-exchangHeatHeatistheenergytransferredbetweenahotobjectandacoldobject.

Temperatureisthedegreeof“hotness”ofanobject.qThighTlowHeatHeatistheenergytransfeIsothermalvs.AdiabaticAnadiabaticprocessinoneinwhichnoheatisexchangedbetweenthesystemanditssurroundings.Anisothermalprocessinoneinwhichtheinitialandfinaltemperaturesarethesame.Isothermalprocessesarenotnecessarilyadiabatic.Isothermalvs.AdiabaticAnadiWorkWorkisanyenergyexchangethatisnotheat.

Workisanyinteractionthatcouldhaveasthesoleeffecttheraisingofaweight.

Work=force·distance1kg1meterWorkWorkisanyenergyexchangStateFunctionvs.PathFunctionAstatefunction

isapropertyofasystemthatdependsonlyonitscurrentstateandnotonhowthatstatewasreached.Apathfunction

dependsonhowthestatewasreached.stateAstateBpath1path2StateFunctionvs.PathFunctiTheFirstLawdU=dw+dq

definestheinternalenergychangeofasystem.Theinternalenergyisafunctionofstate.Corollary:Energyisconservedinanisolatedsystem.stateAstateBwqwqTheFirstLawdU=dw+dq

defWorkofExpansion/Compressiongasdzpexpex=externalpressureA=pistonareadz=displacementdV=-Adz=volumechangeforthegasdw=Fdz

dw=-pexdVAWorkofExpansion/CompressiongReversibleChangesAreversiblechange

isonethatcanbereversedbyaninfinitesimalmodificationofavariable.

Inareversibleexpansionorcompression,pex=pgaspexpgasReversibleChangesAreversibleIrreversibleChangesAnirreversiblechange

isonethatisnotreversible.

Inanirreversibleexpansion,pex<pgas

Inanirreversiblecompression,pex>pgaspexpgaspexpgasIrreversibleChangesAnirreverIndicatorDiagram:compressionpexViVfT=273KadditionalirreversibleworkreversibleworkIndicatorDiagram:compressionIsothermalReversibleWorkIsothermalReversibleWorkIsothermalIrreversibleWorkIsothermalIrreversibleWorkAdiabaticExpansiondq=0dU=dwforanidealgas,

CVdT=-pexdVifreversible,

pex=p=nRT/Vtherefore,

CV(dT/T)=-nR(dV/V)qqwAdiabaticExpansiondq=0qqwReversibleAdiabaticExpansionReversibleAdiabaticExpansionReversibleAdiabaticExpansionReversibleAdiabaticExpansionReversibleAdiabaticExpansionReversibleAdiabaticExpansionIrreversibleAdiabaticExpansionIrreversibleAdiabaticExpansiArgon:Adiabatsvs.IsothermsadiabatisothermArgon:Adiabatsvs.IsothermsaEnthalpyandHeatEnthalpyisdefined

H=U+pV

dH=dU+pdV+Vdp

atconstantp,

dH=dU+pdVdH=dqpEnthalpyandHeatEnthalpyisdHeatCapacity:Cv,mTUslope=CVHeatCapacity:Cv,mTUslope=CHeatCapacity:Cp,mTHslope=CpHeatCapacity:Cp,mTHslope=CTemperatureDependenceofCp,mCp,m=a+bT+c/T2inJ/mole

TemperatureDependenceofCp,mVariationofHwithTemperatureVariationofHwithTemperaturHess’sLawTheenthalpychangeforanoverallreactionisthesumoftheenthalpychangesoftheindividualreactionsintowhichareactionmaybedivided.

DHA-C=

DHA-B+DHB-CA®BB®CA®CreactantsAproductsCHess’sLawTheenthalpychangeStandardEnthalpyofFormationThestandardreactionenthalpyDHr0

isthechangeinenthalpywhenreactantsintheirstandardstateschangetoproductsintheirstandardstates.Thestandardenthalpyofformation

ofasubstanceDHf0isthestandardreactionenthalpyfortheformationofthecompoundfromitselementsintheirreferencestates.StandardEnthalpyofFormation

DHf0

ExamplesAceticAcid

2C(gr)+O2(g)+2H2(g)®CH3COOH(l)

AmmoniumNitrate

N2(g)+2H2(g)+3/2O2(g)®NH4NO3(s)

SodiumChloride

Na(s)+1/2Cl2(g)®NaCl(s)

DHf0ExamplesAceticAcid

2C(Hess’LawandDHf0

Forthereaction2A+B®3C+D,

DH0=3DHf0(C)+DHf0(D)-2DHf0(A)-DHf0(B)

ForthegeneralreactionSnJJ=0,

DH0=SnJDHf0(J)

GivenDHf0valuesforallthereactantsandproducts,DH0maybecalculatedforanyreaction.

Hess’LawandDHf0ForthereaTemperatureDependenceofDrHReactants(T2)Reactants(T1)Products(T2)Products(T1)DrH(T1)DrH(T2)DHRDHPDrH(T2)=DHR+DrH(T1)+DHPTemperatureDependenceofDrHRKirchhoff’sLawKirchhoff’sLawTheFirstLawTheMachineryTheFirstLawTheMachineryExactDifferentialsdxdydzExactDifferentialsdxdydzInternalEnergyChangesInternalEnergyChanges

ThermodynamicEq’nofState

ThermodynamicEq’nofStateExpansionCoefficientExpansionCoefficientIsothermalCompressibilityIsothermalCompressibilityTableofandTTableofandTCpandCVCpandCV物理化学英文2The-First-Law课件PhysicalChemistryTheFirstLawPhysicalChemistryTheFirstLawTheConceptsTheFirstLawTheConceptsSystemandSurroundingsSystem-thepartoftheworldinwhichwehaveaspecialinterest.

Surroundings-wherewemakeourobservations.systemsurroundingsSystemandSurroundingsSystemTypesofSystemsOpen-exchangesmatterandenergywithsurroundings.

Closed-exchangesonlyenergywithsurroundings.

Isolated-nointerchangewithsurroundings.EnergyEnergyMatterTypesofSystemsOpen-exchangHeatHeatistheenergytransferredbetweenahotobjectandacoldobject.

Temperatureisthedegreeof“hotness”ofanobject.qThighTlowHeatHeatistheenergytransfeIsothermalvs.AdiabaticAnadiabaticprocessinoneinwhichnoheatisexchangedbetweenthesystemanditssurroundings.Anisothermalprocessinoneinwhichtheinitialandfinaltemperaturesarethesame.Isothermalprocessesarenotnecessarilyadiabatic.Isothermalvs.AdiabaticAnadiWorkWorkisanyenergyexchangethatisnotheat.

Workisanyinteractionthatcouldhaveasthesoleeffecttheraisingofaweight.

Work=force·distance1kg1meterWorkWorkisanyenergyexchangStateFunctionvs.PathFunctionAstatefunction

isapropertyofasystemthatdependsonlyonitscurrentstateandnotonhowthatstatewasreached.Apathfunction

dependsonhowthestatewasreached.stateAstateBpath1path2StateFunctionvs.PathFunctiTheFirstLawdU=dw+dq

definestheinternalenergychangeofasystem.Theinternalenergyisafunctionofstate.Corollary:Energyisconservedinanisolatedsystem.stateAstateBwqwqTheFirstLawdU=dw+dq

defWorkofExpansion/Compressiongasdzpexpex=externalpressureA=pistonareadz=displacementdV=-Adz=volumechangeforthegasdw=Fdz

dw=-pexdVAWorkofExpansion/CompressiongReversibleChangesAreversiblechange

isonethatcanbereversedbyaninfinitesimalmodificationofavariable.

Inareversibleexpansionorcompression,pex=pgaspexpgasReversibleChangesAreversibleIrreversibleChangesAnirreversiblechange

isonethatisnotreversible.

Inanirreversibleexpansion,pex<pgas

Inanirreversiblecompression,pex>pgaspexpgaspexpgasIrreversibleChangesAnirreverIndicatorDiagram:compressionpexViVfT=273KadditionalirreversibleworkreversibleworkIndicatorDiagram:compressionIsothermalReversibleWorkIsothermalReversibleWorkIsothermalIrreversibleWorkIsothermalIrreversibleWorkAdiabaticExpansiondq=0dU=dwforanidealgas,

CVdT=-pexdVifreversible,

pex=p=nRT/Vtherefore,

CV(dT/T)=-nR(dV/V)qqwAdiabaticExpansiondq=0qqwReversibleAdiabaticExpansionReversibleAdiabaticExpansionReversibleAdiabaticExpansionReversibleAdiabaticExpansionReversibleAdiabaticExpansionReversibleAdiabaticExpansionIrreversibleAdiabaticExpansionIrreversibleAdiabaticExpansiArgon:Adiabatsvs.IsothermsadiabatisothermArgon:Adiabatsvs.IsothermsaEnthalpyandHeatEnthalpyisdefined

H=U+pV

dH=dU+pdV+Vdp

atconstantp,

dH=dU+pdVdH=dqpEnthalpyandHeatEnthalpyisdHeatCapacity:Cv,mTUslope=CVHeatCapacity:Cv,mTUslope=CHeatCapacity:Cp,mTHslope=CpHeatCapacity:Cp,mTHslope=CTemperatureDependenceofCp,mCp,m=a+bT+c/T2inJ/mole

TemperatureDependenceofCp,mVariationofHwithTemperatureVariationofHwithTemperaturHess’sLawTheenthalpychangeforanoverallreactionisthesumoftheenthalpychangesoftheindividualreactionsintowhichareactionmaybedivided.

DHA-C=

DHA-B+DHB-CA®BB®CA®CreactantsAproductsCHess’sLawTheenthalpychangeStandardEnthalpyofFormationThestandardreactionenthalpyDHr0

isthechangeinenthalpywhenreactantsintheirstandardstateschangetoproductsintheirstandardstates.Thestandardenthalpyofformation

ofasubstanceDHf0isthestandardreactionenthalpyfortheformationofthecompoundfromitselementsintheirreferencestates.StandardEnthalpyofFormation

DHf0

ExamplesAceticAcid

2C(gr)+O2(g)+2H2(g)®CH3COOH(l)

AmmoniumNitrate

N2(g)+2H2(g)+3