Reversible Reactions
Year 10 (IGCSE) ⚗️ Chemical Reactions Describe dynamic equilibrium; apply Le Chatelier's principle.
⇌ Dynamic Equilibrium
In reversible reactions at equilibrium, forward and reverse rates are equal and concentrations remain constant (but not equal).
Dynamic Equilibrium
$$\text{Rate}_\text{forward} = \text{Rate}_\text{reverse}$$ Equilibrium is dynamic — both reactions continue, but no net change in concentration occurs.
📐 Le Chatelier's Principle
If equilibrium is disturbed, it shifts in the direction that opposes the change.
| Change | Equilibrium shift |
|---|---|
| ↑ Temperature | Towards endothermic direction |
| ↑ Pressure | Towards fewer gas molecules |
| ↑ Concentration of reactant | Towards products |
| Catalyst added | No shift (just faster equilibrium) |
🏭 Applied: N₂ + 3H₂ ⇌ 2NH₃
↑ Pressure: 4 mol gas → 2 mol → shifts right (more NH₃) ✓
↑ Temperature: exothermic forward → shifts left (less NH₃) ✗
Catalyst: no shift in position; equilibrium reached faster.
↑ Temperature: exothermic forward → shifts left (less NH₃) ✗
Catalyst: no shift in position; equilibrium reached faster.
Ready to test yourself? Click the Quiz tab above to practise questions on this topic!
Interactive Demonstration — Reversible Reactions
See how Le Chatelier's principle shifts equilibrium position.
⇌ Equilibrium Shift Predictor
Calculate the equilibrium constant Kc from concentrations.