6.2.3 Equilibrium

In a reversible reaction, the reaction can proceed in both the forward and reverse directions. When the forward and reverse reactions occur at exactly the same rate, the system is said to be at equilibrium.

Reversible Reactions and Equilibrium

Reversible reactions can reach a state of equilibrium when the forward and reverse reactions occur simultaneously.

• Equilibrium is a dynamic state, meaning that the reactions continue to occur, but with no net change in the concentrations of the reactants and products.
• At equilibrium, the concentrations of the reactants and products remain constant over time, although the individual particles continue to collide and undergo reactions.

The Equilibrium Position

The equilibrium position refers to the relative concentrations of the reactants and products at equilibrium. The equilibrium position can be shifted towards the products (right) or the reactants (left) by changing the conditions of the system, such as temperature, pressure, or concentration.

Factors Affecting Equilibrium

• Changes in Temperature: Increasing the temperature favours the endothermicA reaction that ‘absorbs’ heat, where the products have greater energy than the reactants. reaction, while decreasing the temperature favours the exothermicA reaction that releases heat, where the products have less energy than the reactants. reaction.
• Changes in Pressure (for gaseous reactions): Increasing the pressure favours the side with fewer moles of gas, while decreasing the pressure favours the side with more moles of gas.
• Changes in Concentration: Increasing the concentration of a reactant or product shifts the equilibrium in the direction that reduces the concentration, while decreasing the concentration shifts the equilibrium in the direction that increases the concentration.

Conclusion

Understanding the concept of equilibrium is crucial in explaining how reversible reactions reach a state where the forward and reverse reactions balance each other. It also highlights the influence of external conditions on the equilibrium position and the ability of the system to respond to changes in those conditions.