110128 - Phase equilibria (Chapter 4 p. 110-117) Gibbs and...

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1 CHM3400 - Lecture 10 Jan 28 Phase equilibria (Chapter 4 p. 110-117) Gibbs and Helmholtz energies Phase equilibria (Gibbs energy): temperature and pressure Phase diagram Degrees of freedom Boiling temperature at reduced pressure
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2 Gibbs and Helmholtz energies G = H - TS Δ G = Δ H - T Δ S Gibbs energy: A = U - TS Δ A= Δ U-T Δ S Helmholtz energy: Difference? G: constant pressure A: constant volume Again more state functions, but actually useful ones.
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3 Reaction spontaneous? Reaction driven by enthalpy or entropy? If a reaction is spontaneous TD, why does it maybe still not take place?
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4 Phase equilibrium: Gibbs energy Example: iceberg in ocean H 2 O(s) H 2 O(l) H 2 O(s) H 2 O(l) G solid = G liquid At the boundary between ice and water: Equilibrium will change if …. changes?
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5 Dependence of G on T and P dG = VdP – SdT Constant pressure : dG = VdP – SdT Constant temperature : dG = VdP – SdT
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6 1. Constant pressure S T G P = δ Molar free energy G Constant pressure = gas liquid solid
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110128 - Phase equilibria (Chapter 4 p. 110-117) Gibbs and...

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