A catalyst added to a reaction mixture speeds up both the forward and the reverse reaction to the same degree.
Explanation level
A catalyst added to a reaction mixture speeds up both the forward and the reverse reaction to the same degree. Thus, the catalyst has no effect on the equilibrium concentrations of the reaction mixture. However, the catalyst is important in enhancing the rate at which the equilibrium is established.
Catalyst has no effect on equilibrium position.
Catalyst speeds up the attainment of equilibrium.
Intermediate Level
Le Chatelier's Principle
Change
Effect on Equilibrium
Add reactant
Shifts to products
Add product
Shifts to reactants
Increase pressure
Shifts to fewer gas molecules
Decrease pressure
Shifts to more gas molecules
Increase temperature
Shifts in endothermic direction
Decrease temperature
Shifts in exothermic direction
Add catalyst
No effect
Examples
Concentration:CO2 + H2 ⇌ CO + H2O - Add CO₂ → shift to products.
Pressure:2SO2 + O2 ⇌ 2SO3 - Increase pressure → shift to right (fewer molecules).
Temperature:2SO2 + O2 ⇌ 2SO3 Δ H = -198 kJ - Increase temperature → shift to left.
N2O4 ⇌ 2NO2 Δ H = +57.2 kJ - Increase temperature → shift to right.
Catalyst: - No effect on equilibrium position.
Important Points
1. Le Chatelier's Principle: System shifts to reduce change.
