Overview
This lecture explains Le Chatelier's Principle, which predicts how changing temperature, pressure, or concentration affects the position of equilibrium in reversible reactions.
Le Chatelier's Principle and Equilibrium
- The position of equilibrium describes the relative amounts of reactants and products at equilibrium.
- If there are more reactants, equilibrium lies to the left; more products means it lies to the right.
- Le Chatelier's Principle states that if conditions change, the equilibrium shifts to counteract the change.
Effect of Temperature Changes
- For an exothermic forward reaction (negative energy change), decreasing temperature favors the forward (exothermic) direction.
- Increasing temperature favors the reverse (endothermic) direction, shifting equilibrium to the left.
Effect of Pressure Changes
- Increasing pressure shifts equilibrium toward the side with fewer gas molecules.
- Decreasing pressure shifts equilibrium toward the side with more gas molecules.
- Example: For ammonia production, more particles are on the left (reactants), fewer on the right (products).
Effect of Concentration Changes
- Increasing the concentration of a reactant shifts equilibrium toward the products to reduce the change.
- Example: Adding more nitrogen drives production of more ammonia.
Key Terms & Definitions
- Le Chatelier's Principle — When a system at equilibrium is disturbed, it shifts to oppose the change.
- Equilibrium Position — The ratio of reactants to products at equilibrium.
- Exothermic Reaction — Releases energy to surroundings.
- Endothermic Reaction — Absorbs energy from surroundings.
- Pressure — Measure of particle numbers per volume.
Action Items / Next Steps
- Review examples of Le Chatelier's Principle applied to different reactions.