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Chapter 20 Lecture 1

# Chapter 20 Lecture 1 - Chapter 20 Thermodynamics Entropy...

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Chapter 20 Thermodynamics: Entropy, Free Energy and the Direction of Chemical Reactions 20-1

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Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions 20 1 The Second Law of Thermodynamics: 20.1 The Second Law of Thermodynamics: Predicting Spontaneous Change 20.2 Calculating the Change in Entropy of a Reaction 20.3 Entropy, Free Energy, and Work 20.4 Free Energy, Equilibrium, and Reaction Direction 20-2
20.1 The Second Law of Thermodynamics Spontaneous changes occur without any external influence Examples: Aging, rusting, heat transfer from hot to cold, expansion of gases into vacuum, etc. Nonspontaneous changes require an external force or energy in order to occur Examples: Refrigeration (heat transfer from cold to hot), Examples: Refrigeration (heat transfer from cold to hot), evacuation of flasks by vacuum pumps, etc. If a process is spontaneous in one direction, it is not spontaneous in the other Example : At -20°C, water freezes spontaneously, but ice does not melt spontaneously: H 2 O(l) H 2 O(s) spontaneous H 2 O(s) H 2 O(l) nonspontaneous Spontaneous does not mean “instantaneous” I h hi d i h h l k 20-3 It has nothing to do with how long a process takes to occur Example: rusting and aging (spontaneous but slow)

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Limitations of the First Law of Thermodynamics The 1 st law of thermodynamics (Chapter 6):
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Chapter 20 Lecture 1 - Chapter 20 Thermodynamics Entropy...

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