Thermodynamics 10. Free energies A and G

# Thermodynamics 10. Free energies A and G - work Important...

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Thermodynamics 10. The Two Free Energies Read in text: Sections 3.5, 3.7, 3.8, 3.9 Problems: 1. 3.16a, p. 114 2. 3.17a 3. 3.18a ------------------------------------------------------------------------------------------------------ Introduce two state functions to monitor spontaneous processes in the SYSTEM. . Helmholtz free energy If V=constant and T=constant, introduce A = U – TS, Prove that dA<0 for spontaneous irreversible processes. A seeks a minimum Also prove dw non-exp =dA=dU-TdS=maximum non-expansion work Gibbs free energy If P=constant and T=constant, introduce G = H – TS Prove that dG<0 for spontaneous irreversible processes. G seeks a minimum Also prove dw non-exp. =dG=dH-TdS=maximum non-expansion

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Unformatted text preview: work Important question: What is ‘free’ about the free energy? Important relations (under what conditions are these valid?) Function A(V,T) : dA=-PdV-SdT Function G(P,T) : dG= VdP-SdT Combined 1-st and 2-nd laws: dU= -pdV+TdS The variation of G with T and P: T G V P G = & , P G S T G = - < & Plot G vs. T and P Variation of G with P (const. T) 2 1 2 1 ( ) ( ) ( ) P P G P G P V P dP = + For the ideal gas: 2 1 2 1 ( ) ( ) ln( / ) G P G P nRT P P = + Variation of G with T (const. P) Start from P G G H S T T G-= - = & Derive the Gibbs-Helmholtz equation 2 P G H T T T = -& (there are several other forms of the GH equation)...
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## This note was uploaded on 05/18/2010 for the course CH 353 taught by Professor Wyatt during the Spring '10 term at University of Texas-Tyler.

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Thermodynamics 10. Free energies A and G - work Important...

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