UNIT OVERVIEW

Chemical equilibrium explains what happens when a reaction can go in both directions at the same time. This is not a contradiction—it is how many reactions work in nature and industry.

In your earlier work on reaction rates, you learned that reactions happen when particles collide with enough energy. Now you will discover what happens when both the forward and reverse reactions occur together.

By the end of this unit, you will be able to:

• Explain the difference between reversible and irreversible reactions
• Describe what dynamic equilibrium means at the particle level
• Apply Le Chatelier's principle to predict how systems respond to changes
• Write equilibrium constant expressions for balanced equations
• Calculate $K_c$ values and interpret what they mean
• Connect equilibrium principles to industrial processes
• Solve equilibrium problems involving concentration changes

Why equilibrium matters:

1. The Haber Process — Ammonia for fertilisers is made using equilibrium principles. This affects food production and the cost of maize meal.