1. Lecture 24 Chemical equilibrium Equilibrium constant Dissociation of diatomic molecule Heterophase reactions

2. Gibbs free energy change Chemical reaction Gibbs free energy change In equilibrium the Gibbs free energy change is zero, therefore

3. Activity Chemical potential with gives

4. Equilibrium constant Defining standard free energy change for the reaction And equilibrium constant for the reaction gives

5. Diatomic molecule Equilibrium constant for the reaction Chemical potential for monoatomic and diatomic gas

6. Diatomic molecule - equilibrium constant

7. Equilibrium pressure expression Equilibrium constant for the reaction Increasing temperature increasing dissociation The major parameter controlling dissociation is D e /kT

8. Heterophase reactions Consider a C =1 (activity of the pure solid phase) K a can be obtained from statistical mechanics (e.q., Einstein model of C solid) or from experiment via