Key learning points

1. Catalysts, pressure, temperature & concentration of solutions can affect equilibrium position of a reversible reaction.
2. If the conditions of a reversible reaction are changed, the equilibrium will move to counteract that change.
3. A catalyst increases the rate at which equilibrium is achieved.
4. Increasing temperature increases the rate of both reactions; equilibrium shifts in favour of the endothermic reaction.
5. Increasing the concentration or pressure of a substance increases the rate of reaction; equilibrium shifts in response.

Keywords

• Le Chatelier’s principle - states that if a dynamic equilibrium is disturbed by changing the conditions, the equilibrium position ‘shifts’ to counteract the change.

• Dynamic equilibrium - occurs in a closed system when the forward and backward reactions of a reversible chemical reaction occur at the same rate; and the concentrations of reactants and products remain constant.

• Equilibrium position - refers to the relative concentrations of reactants and products in a reversible reaction at equilibrium.

• Reaction rate - is the speed with which a chemical reaction takes place, measured by the amount of a reactant used or amount of product formed in a given time.

Common misconception