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Unformatted text preview: Chemistry 111 Chemistry 111 Recitation # 9 November 15, 2005 More Thermodynamics and Thermochemistry … • Entropy (S) Æ Entropy = measure of disorder; related to probability Æ S = k B ln(W) Å Entropy is related to the number of microstates available to a particular m a c r o s t a t e • Second Law of Thermodynamics: Δ S universe ≥ 0 Æ Δ S universe = Δ S system + Δ S surroundings • Third Law of Thermodynamics: S Æ 0 as T Æ for pure crystals of substances Æ S o ≠ 0 for elements in their standard state • Gibbs Free Energy (G) Æ Δ G = -T Δ S universe Æ G = H – TS Æ Δ G = Δ H - T Δ S Æ constant T and P • Spontaneous reactions Æ if Δ S universe > 0 a process is spontaneous Æ if Δ G < 0 a process is spontaneous • Physical Processes Æ Δ G = Δ H - T Δ S • Chemical Processes Æ Δ S = Σ S o (products) – Σ S o (reactants) Æ Δ G = Σ Δ G o f (products) – Σ Δ G o f (reactants) Δ G = Δ H – T Δ S Δ H sys = Δ H Δ S sys = Δ S Δ G Δ S universe Spontaneous? negative (exothermic) positive (disorder increases) negative positive Yes! at all T's positive (endothermic) negative (order increases) positive negative No!...
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This note was uploaded on 02/08/2010 for the course CHEM 111 taught by Professor Kenney during the Spring '08 term at Case Western.
- Spring '08