Physical chemistr Physical Chemistry Cheng Xuan February 2004, Spring Semester
Physical Chemistry Cheng Xuan February 2004, Spring Semester Physical Chemistry
Physical Chemistry Chapter 4 Material equilibrium rReaction: Equilibrium with respect to conversion of one set of chemical species to another set Phase: Equilibrium with respect to transport of matter between phase of the system without conversion of one species to another
Chapter 4 Material Equilibrium Equilibrium with respect to conversion of one set of chemical species to another set Reaction: Equilibrium with respect to transport of matter between phase of the system without conversion of one species to another Phase: Physical Chemistry
Physical Chemistry Material Equilibrium Entropy and Equilibrium First law: The internal energy(U to identify permissible changes Second law: The entropy(S) to identify the spontaneous changes among those permissible changes The entropy(s) of an isolated system increases in the course of a spontaneous change: AStot >0 The criterion for equilibrium in an isolated system maximization of the system's entropy S syst+s surr a maximum at equilibrium (4.2)
Entropy and Equilibrium The internal energy (U) to identify permissible changes First law: The entropy (S) to identify the spontaneous changes among those permissible changes Second law: Material Equilibrium The entropy (S) of an isolated system increases in the course of a spontaneous change: Stot >0 The criterion for equilibrium in an isolated system: maximization of the system’s entropy S Physical Chemistry Ssyst + Ssurr a maximum at equilibrium (4.2)*
Physical Chemistry Material Equilibrium Entropy and Equilibrium trey (46) ds= rev S≥ (48) dq=dU-dw dq stds d q=du-dw sTds du<Tas+aw
Entropy and Equilibrium dq TdS T dq dS irrev (4.6) T dq dS rev = (4.7) T dq dS (4.8) dU TdS +dw (4.9) dq = dU - dw TdS Physical Chemistry Material Equilibrium dq = dU - dw
Physical Chemistry Material Equilibrium The gibbs and Helmholtz Energies dU≤T+dh =:equilibrium (4.9) dU≤T+SdT-ST+dbw (4.10) du s d(tsy-sar+ dw d(U-tss-sdr+ dw (4.12) P-v work only tU-Ss-盛-pm (4.13) at constant T and V dT=0. dv=O d(U-TS)≤0 P-V work only (4.14)
The Gibbs and Helmholtz Energies dU TdS + SdT – SdT + dw (4.10) dU d(TS) – SdT + dw (4.11) d(U – TS) – SdT + dw (4.12) d(U – TS) – SdT - PdV (4.13) at constant T and V, dT=0, dV=0 d(U – TS) 0 P-V work only (4.14) dU TdS + dw =: equilibrium (4.9) P-V work only Physical Chemistry Material Equilibrium