物理化学英文3The-Second-Law课件

,*,Click to edit Master title style,Click to edit Master text styles,Second Level,Third Level,Fourth Level,Fifth Level,Physical Chemistry,The Second Law,Physical Chemistry,The Second Law,The Concepts,The Second LawThe Concepts,The Laws of Thermodynamics,First Law,You cant get something for nothing,.,Second Law,You cant even break even.,The Laws of ThermodynamicsFirs,Heat Engines,A,heat engine,converts heat into work.,T,h,=,temperature of heat source,T,c,=,temperature of heat sink,q,h,=,heat supplied,q,c,=,heat released,w=,work produced,T,h,T,c,Engine,q,h,q,c,w,Heat EnginesA heat engine conv,Efficiency of Heat Engines,An engine operates in a cycle;,D,U=0and,|w|,=q,h,-|q,c,|,efficiency is given by,e,=|w|/q,h,e,=1-|q,c,|,/q,h,|q,c,|0 implies,e,1,You cant get,something for,nothing.,You cant even,break even.,Efficiency of Heat EnginesAn e,The Second Law(Kelvin),No process is possible in which the sole result is the absorption of heat from a reservoir and its,complete,conversion into work.,In other words,|w|dq/T,for an irreversible change,Corollary:For an isolated system,dS=0,for a reversible change,dS 0,for an irreversible change,The Second Law(Clausius)The e,Carnot Cycle,isothermal:100 K,adiabatic,isothermal:200 K,adiabatic,Carnot Cycleisothermal:100 Ka,Carnot Efficiency,D,S=,D,S,engine,+,D,S,surr,0,but,D,S,engine,=0,D,S,surr,=-(q,h,/T,h,)+(q,c,/T,c,),0,q,c,/q,h,T,c,/T,h,e,=|w|/q,h,=1-|q,c,|/q,h,e,1-(T,c,/T,h,),Carnot EfficiencyDS=DSengine,Spontaneity and Equilibrium,A spontaneous change is an irreversible one.,Therefore any change for which dSdq/T will occur spontaneously,In an,isolated,system,any change for which dS0 will occur spontaneously.,In an isolated system at equilibrium,the entropy is at a maximum.,Spontaneity and EquilibriumA s,Spontaneous Heat Transfer,T,h,T,c,dq,Spontaneous Heat TransferThTcd,Entropy at the Molecular Level,D,S0 reflects an increase in W,the,weight,of the configuration,W,initial,=6,W,final,=28,Entropy at the Molecular Level,D,S for Phase Changes,Melting,T=T,m,=constant,q=,D,H,fus,D,S=,D,H,fus,/T,m,Boiling,T=T,b,=constant,q=,D,H,vap,D,S=,D,H,vap,/T,b,DS for Phase ChangesMeltingBo,D,S for a Temperature Change,Assume a reversible path at constant pressure.Then,DS for a Temperature ChangeAss,D,S for an Ideal Gas Isotherm,DS for an Ideal Gas Isotherm,Third Law of Thermodynamics,Nernst Heat Theorem:,D,S,0 as T,0.,Arbitrary convention:The entropy of an element in its pure crystalline form is zero at T=0.,Third Law:Therefore the entropy of any perfect crystalline substance is zero at T=0.,Third Law of ThermodynamicsNer,Third Law Entropies,Third Law Entropies,Third Law Entropy of Pb(s),T/K,C,p,/T,Third Law Entropy of Pb(s)T/,Numerical Integration,Trapeziodal Rule:,divide total area into trapezoids,trapezoid area=,(y,2,+y,1,)(x,2,-x,1,),integral equals sum of all trapezoid areas,y,1,y,2,x,2,-x,1,y(x),Numerical IntegrationTrapeziod,Debye Extrapolation,Debye Extrapolation,Helmholtz Free Energy,Definition:A,U-TS,dA,T,=dU-TdS,dA,T,dU-dq,dA,T,dw,D,A=w,max,dA,T,V,0,i.e.for constant T and V,A is a minimum at equilibrium.,Helmholtz Free EnergyDefinitio,Gibbs Free Energy,Definition:G,U-TS+pV,dG,T,p,=dU-TdS+pdV,dG,T,p,dU-dq-w,dG,T,p,dw,e,D,G=w,max,e,If the only work is expansion/compression,dG,T,p,0,i.e.for constant T and p,G is a minimum at equilibrium.,Gibbs Free EnergyDefinition:,The Second Law,The Machinery,The Second LawThe Machinery,The Fundamental Equations,dU=TdS-pdV,dH=TdS+Vdp,dA=-SdT-pdV,dG=-SdT+Vdp,The Fundamental EquationsdU=,Maxwell Relations-Derivation,Maxwell Relations-Derivation,Maxwell Relations-Summary,Maxwell Relations-Summary,Thermodynamic Eqn.of State,Thermodynamic Eqn.of State,Variation of G with Temperature,gas,liquid,solid,T,G,Variation of G with Temperatur,Variation of G with Pressure,gas,liquid,solid,p,G,Variation of G with Pressurega,Gibbs-Helmholz Equation,Gibbs-Helmholz Equation,Temperature dependence of,D,G,Temperature dependence of DG,Pressure dependence of,D,G,Pressure dependence of DG,Composition Dependence,Composition Dependence,Chemical Potential,m,i,is the slope of G,i,vs.n,i,for a pure substance G=nG,m,and,m=,G,m,=constant,for a mixture,G,i,vs.n,i,is not linear and,m,is not constant,n,n,i,G,G,pure substance,mixture,Chemical Potentialmi is the sl,Ideal Gas Mixture Model,Ideal Gas Mixture Model,Equilibrium and,m,Consider the reaction A=B,At equilibrium dG=0,dG,p,T,=,m,A,dn,A,+,m,B,dn,B,but dn,A,=-dn,B,dG,p,T,=(,m,A,-,m,B,)dn,B,therefore,at equilibrium,m,A,=,m,B,Equilibrium and mConsider the,Real Gases,Real Gases,Argon Fugacity Coefficient,f,p/atm,attractive,repulsive,273 K,Argon Fugacity Coefficientfp/,Fugacity Coefficient,Fugacity Coefficient,Ammonia Fugacity Integral,p/atm,(Z-1)/p,Area=ln,f,Ammonia Fugacity Integralp/at,物理化学英文3The-Second-Law课件,