# Chapt. 6: Chemical Equilibrium

# Chapt. 6: Chemical Equilibrium

by Terrence Oas
# 1. The Equilibrium Condition

## 1.1. How a reaction reaches equilibrium

## 1.2. Characteristics of chemical equilibrium

## 1.3. Equilibria are dynamic

# 2. The Equilibrium Constant

## 2.1. Law of mass action

## 2.2. Characteristics of the equilibrium expression

## 2.3. Equilibria in ammonia synthesis

## 2.4. Equilibrium position

# 3. Equilibrium Expressions Involving Pressures

## 3.1. Ideal gas law

## 3.2. Equilibrium partial pressures

## 3.3. Kp vs. K

# 4. The Concept of Activity

## 4.1. The reference state

## 4.2. For a gas, 1 atm

## 4.3. Definition of activity

# 5. Heterogeneous Equilibria

## 5.1. Phases: gas, solid, liquid

## 5.2. Heterogeneous Equilibria: between multiple phases

## 5.3. Equilibrium constant for heterogeneous equilibria

## 5.4. Activity of pure phases (solids or liquids)

# 6. Applications of the Equilibrium Constant

## 6.1. Predictions based on the equilibrium constant

## 6.2. Extent of reaction

## 6.3. Reaction quotient (Q)

## 6.4. Calculating equilibrium pressures and concentrations

# 7. Solving Equilibrium Problems

# 8. Le Châtelier's Principle

## 8.1. Effect of a change in conditions on equilibria

## 8.2. Effect of a change in concentration

## 8.3. Effect of a change in pressure

# 9. Equilibria Involving Real Gases

## 9.1. Non-ideality

## 9.2. How to correct Kp for non-ideality

# 10. Equilibria are dynamic but may be so slow that []s appear not to change

# 11. K is meaningful only at equilibrium

## 11.1. Can't be = 0 or 1/0

## 11.2. Large K (>>1) means products favored

## 11.3. Small K (<<1) means reactants favored

# 12. Activity is a way to compare the amount of a reactant or product to their standard state and make K unit-less

# 13. Partial pressures sum to total pressure

# 14. Acitivity of pure solid or liquid = 1

# 15. Q describes the position of a rxn not necessarily at equilibrium

# 16. ICE tables help organize equilibrium problems

# 17. Try to make x in the ICE table small. This simplifies the math!

# 18. You can do "math" with chemical equations

## 18.1. Adding c.e. means multiplying K

## 18.2. Multiplying c.e. by n means taking K^n

## 18.3. Reversing c.e. means taking 1/K

# 19. "Stress" on an equilibrium shifts reaction in direction that minimizes change

## 19.1. Add reactant (R) or product (P): rxn shifts to consume it Remove R or P: rxn shifts to replace it

## 19.2. Decrease the volume: rxn shifts to the side with the smallest n

## 19.3. Treat energy as R or P to predict effect of T on K

# 20. Activity coefficients correct for interactions between species