Overview
This lecture explains how changing temperature affects reversible reactions at equilibrium, using Le Chatelier's Principle, with a focus on exothermic and endothermic reactions.
Le Chatelier's Principle and Equilibrium
- Le Chatelier's Principle states a system at equilibrium will adjust to counteract any changes in conditions.
- Changing concentration affects equilibrium position; this video focuses on temperature changes.
Exothermic and Endothermic Reactions
- A reaction is exothermic if it releases energy and increases the system's temperature.
- If the forward reaction is exothermic, the reverse reaction must be endothermic, which absorbs energy and lowers temperature.
- The direction of exothermic or endothermic reactions varies; exam questions will provide this information.
Effect of Temperature Change on Equilibrium
- Increasing temperature shifts equilibrium toward the endothermic direction to absorb added heat.
- For the reaction NO₂ ⇌ N₂O₄, increasing temperature shifts equilibrium to the left (more NO₂, less N₂O₄), as the reverse reaction is endothermic.
- Decreasing temperature shifts equilibrium toward the exothermic direction to release heat.
- For NO₂ ⇌ N₂O₄, decreasing temperature shifts equilibrium to the right (more N₂O₄, less NO₂), as the forward reaction is exothermic.
Key Terms & Definitions
- Equilibrium — The state where the rates of the forward and reverse reactions are equal in a reversible reaction.
- Le Chatelier's Principle — When a system at equilibrium is disturbed, it shifts to counteract the disturbance.
- Exothermic Reaction — A reaction that releases energy to its surroundings, raising temperature.
- Endothermic Reaction — A reaction that absorbs energy from its surroundings, lowering temperature.
- Reversible Reaction — A reaction where the products can react to reform the reactants.
Action Items / Next Steps
- Review questions on the effect of temperature on reversible reactions in the revision workbook.
- Rewatch the video if clarification is needed.