Summary
Reversible reactions are those where the products can react to form the reactants again, occurring in both forward and reverse directions. Equilibrium is reached when the rate of the forward reaction equals the rate of the backward reaction, with concentrations remaining constant in a closed system.
- Reversible Reaction — a reaction where products can reform reactants Example: NH4Cl (s) ⇌ NH3 (g) + HCl (g)
- Dynamic Equilibrium — state where forward and backward reactions occur at the same rate Example: Concentrations of reactants and products remain constant
- Le Chatelier's Principle — principle that predicts how a change in conditions affects equilibrium Example: Increasing pressure shifts equilibrium towards fewer gas molecules
Exam Tips
Key Definitions to Remember
- Reversible Reaction: A reaction that can proceed in both forward and reverse directions
- Dynamic Equilibrium: When the rate of the forward reaction equals the rate of the backward reaction
- Le Chatelier's Principle: Describes how equilibrium shifts in response to changes in concentration, pressure, or temperature
Common Confusions
- Equilibrium does not mean reactions stop; they continue at the same rate
- Equilibrium can only be achieved in a closed system
Typical Exam Questions
- What is a reversible reaction? A reaction where products can reform reactants
- How does increasing pressure affect equilibrium in a gaseous reaction? It shifts towards the side with fewer gas molecules
- What happens to equilibrium if temperature is increased in an exothermic reaction? It shifts towards the endothermic direction
What Examiners Usually Test
- Understanding of dynamic equilibrium
- Application of Le Chatelier's Principle to predict changes in equilibrium
- Ability to write and interpret reversible reaction equations