Chemical Change: Reversible Reactions

• Chemical reactions may be reversible, which means the products of the reaction can react together to produce the original reactants.

• A reversible reaction can proceed in both directions, which are called the forward reaction (from reactants to products) and backward reaction (from products to reactants).

• In a closed system, reversible reactions reach an equilibrium state, where the concentrations of the reactants and products remain constant over time.

• At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction.

• The position of the equilibrium can be affected by changes in temperature, pressure, or concentration.

• Increasing the temperature shifts the equilibrium in the direction of the endothermic reaction. Decreasing the temperature shifts the equilibrium in the direction of the exothermic reaction.

• Increasing the pressure shifts the equilibrium in the direction of the side with fewer molecules of gas, and decreasing the pressure shifts the equilibrium in the direction of the side with more molecules of gas.

• Increasing the concentration of reactants shifts the equilibrium towards products, and increasing the concentration of the products shifts the equilibrium towards reactants.

• Le Chatelier’s Principle explains how the position of equilibrium shifts in response to changes. It states that if a change is imposed on a system at equilibrium, the system will adjust itself to counteract the change.

• The principle of conservation of matter applies to reversible reactions since no atoms are created or destroyed, i.e., the total mass of the reactants equals the total mass of the products.

• Haber process, which is used in industry to manufacture ammonia, and Contact process, used to produce sulphuric acid, are both examples of reversible reactions.