Chapter 18

# Chapter 18 - Chpater 18: Thermodynamics I. Entropy a....

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Chpater 18: Thermodynamics I. Entropy a. Affected by phase (solid, liquid, and gas) i. Solid = small # of arrangements = low Entropy 1. Melting a solid a. Going from low entropy to large entropy b. S > 0 ii. Liquid = more # arrangements = entropy is larger iii. Gas = many # arrangements = Large Entropy b. Gas volume i. As volume increases and pressure decreases = larger entropy 1. S > 0 ii. Same as solution 1. Larger volume = larger # possible arrangements c. Mixing i. Increase in S because each part can occupy a larger volume d. Temperature i. Low T = molecules move slowly = small S ii. High T = molecules move faster = larger S iii. S increases with increasing T e. S = R[ln(W)] i. W = # of arrangements ii. R = 8.31 J/mol • K iii. S = J/mol • K or J/K iv. 0<S<∞ 1. no negative entropies for a well defined system v. Third Law of Thermodynamics 1. At 0 K (no motion) is a pure crystalline solid, W = 1 and S = 0 2. Each substance has an absolute entropy II. Standard Condition a. 1 atm or 1 M

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## This note was uploaded on 01/27/2011 for the course CHEM 0120 taught by Professor Golde during the Spring '07 term at Pittsburgh.

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Chapter 18 - Chpater 18: Thermodynamics I. Entropy a....

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