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Unformatted text preview: Lecure 5: The Second and Third Laws of Thermodynamics • Reading: Zumdahl 10.5, 10.6 • Outline – Definition of the Second Law – Determining ∆ S – Definition of the Third Law The Second Law • The Second Law: In any spontaneous process , there is always an increase in the entropy of the universe . • From our definitions of system and surroundings: ∆ S universe = ∆ S system + ∆ S surroundings The Second Law (cont.) • Three possibilities: – If ∆ S univ > 0…..process is spontaneous – If ∆ S univ < 0…..process is spontaneous in opposite direction. – If ∆ S univ = 0….equilibrium • Here’s the catch: We need to know ∆ S for both the system and surroundings to predict if a reaction will be spontaneous! The Second Law (cont.) • Consider a reaction driven by heat flow from the surroundings at constant P. – Exothermic Process: ∆ S surr = heat/T – Endothermic Process: ∆ S surr = -heat/T • Heat transferred = q P,surr = - q P,system=- ∆ H sys...
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This note was uploaded on 01/18/2012 for the course CHEM 152A taught by Professor Chiu during the Winter '12 term at University of Washington.
- Winter '12