How does temperature affect a reversible reaction at equilibrium?

Temperature affects a reversible reaction at equilibrium by shifting the equilibrium position and changing the equilibrium constant.

In a reversible reaction, the forward and reverse reactions occur simultaneously and at the same rate when the system is at equilibrium. However, this balance can be disturbed by changes in conditions such as temperature. According to Le Chatelier's principle, if a system at equilibrium is subjected to a change, the system will adjust itself to counteract that change.

When the temperature of a system at equilibrium is increased, the system will respond by favouring the endothermic reaction (the reaction that absorbs heat) to reduce the temperature. This is because the endothermic reaction uses up the excess heat. Conversely, if the temperature is decreased, the system will favour the exothermic reaction (the reaction that releases heat) to increase the temperature. This is because the exothermic reaction produces heat, compensating for the heat that was lost.

In addition to shifting the equilibrium position, changes in temperature also affect the equilibrium constant (Kc or Kp) of the reaction. The equilibrium constant is a measure of the ratio of the concentrations of the products to the reactants at equilibrium. If the temperature is increased, the equilibrium constant for an endothermic reaction will increase, indicating that more products are formed. Conversely, for an exothermic reaction, the equilibrium constant will decrease, indicating that less products are formed. If the temperature is decreased, the opposite effects will occur.

In summary, temperature plays a crucial role in determining the direction and extent of a reversible reaction at equilibrium. It's important to remember that these changes are a response to restore equilibrium, demonstrating the system's natural tendency to maintain balance.