230_Sp10_L11_post-1(1)

230_Sp10_L11_post-1(1) - CHEM 230 Sp10 Lecture 11 Chapter...

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Unformatted text preview: CHEM 230 Sp10 Lecture 11 Chapter 7: Gibbs Free Energy 1) Laws of thermodynamics 2) Δ G and spontaneity 3) Calculating Δ G Session ID 230 The Laws of Thermodynamics First Law: Δ U = q + w (internal energy of an isolated system is constant) Second Law: Δ S Tot = Δ S sys + Δ S surr ≥ Δ S Tot > 0 spontaneous, irreversible = 0 equilibrium, reversible < 0 nonspontaneous Third Law: S → 0 as T → 0K Entropy: Reversible vs. Irreversible Equilibrium Spontaneous Which process violates the 2 nd Law of Thermodynamics? A. A refrigerator maintaining a temperature that is lower than the temperature in the room B. Purifying a gas by effusion C. Life D. One side of a coin spontaneously becoming much warmer than the other side Concept Question Which process violates the 2 nd Law of Thermodynamics? A. A refrigerator maintaining a temperature that is lower than the temperature in the room B. Purifying a gas by effusion C. Life D. One side of a coin spontaneously becoming much warmer than the other side A & C require input of energy, while B is energy neutral D implies heat was flowing from cold to hot or a net decrease in entropy Δ S tot leads to Gibbs free energy Δ S Tot = Δ S sys + Δ S surr Δ S Tot = Δ S sys- Δ H/T-T Δ S Tot = -T Δ S sys + Δ H Δ G = -T Δ S sys + Δ H Δ G = Δ H -T Δ S sys Δ S Tot > ; Δ G < 0 spontaneous Δ S Tot = ; Δ G = 0 equilibrium Δ S Tot < ; Δ G > 0 not spontaneous Δ G = - T Δ S tot Multiply by -T Gibbs Free Energy Tell if process is spontaneous State function Bonus Calculate non-expansion work How temperature change affects spontaneity Drawbacks Constant Temperature and Pressure Δ G o = Δ H o-298K* Δ S o sys Δ G = Δ H o-T Δ S o sys What is the Gibbs Free Energy for two moles of ice melting at 273 K?...
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This note was uploaded on 01/24/2012 for the course PCHEM 230 taught by Professor Gottfried during the Fall '11 term at University of Michigan.

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230_Sp10_L11_post-1(1) - CHEM 230 Sp10 Lecture 11 Chapter...

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