Overview
This lesson explains how changing the concentration of reactants or products affects a reversible reaction at equilibrium, using Le Chatelier’s Principle.
Reversible Reactions and Equilibrium
- Some chemical reactions are reversible, meaning products can reform into reactants.
- In a sealed container, the reaction reaches equilibrium when the forward and reverse reactions occur at the same rate.
- At equilibrium, the concentrations of reactants and products remain constant, but both reactions continue to happen.
Changing Concentration and System Response
- If the conditions (such as concentration) change, the system responds to counteract the change.
- This behavior is described by Le Chatelier’s Principle: a system at equilibrium shifts to reduce the effect of an applied change.
Effect of Changing Concentration (Examples)
- Increasing the concentration of a reactant (e.g., NO₂): more product (e.g., N₂O₄) forms until equilibrium is restored.
- Decreasing the concentration of a product (e.g., N₂O₄): more reactant (e.g., NO₂) reacts to produce more product until equilibrium is reached.
- Increasing the concentration of a product (e.g., N₂O₄): more product turns back into reactant (NO₂) until equilibrium is restored.
Key Terms & Definitions
- Reversible Reaction — a reaction where products can convert back into reactants.
- Equilibrium — the state where forward and reverse reactions occur at the same rate and concentrations remain constant.
- Le Chatelier’s Principle — if a system at equilibrium is disturbed, it shifts to counteract the disturbance.
Action Items / Next Steps
- Practice questions on the effect of concentration changes in reversible reactions using the recommended revision workbook.