An increase in temperature affects the equilibrium constant expression but does not change its value. To understand this, let's first clarify what the equilibrium constant represents.
The equilibrium constant (K) is a numerical value that characterizes the extent of a chemical reaction at equilibrium. It is determined solely by the stoichiometry of the balanced chemical equation and is constant at a given temperature.
When the temperature is increased, the system absorbs energy and the reaction proceeds to counteract the temperature rise, either by absorbing or releasing heat. This shift in the reaction affects the equilibrium concentrations of the reactants and products, leading to a change in the equilibrium constant expression. Specifically, the concentrations of the reactants and products in the equilibrium constant expression will be altered due to the temperature change.
However, even though the equilibrium constant expression is modified, the value of the equilibrium constant (K) itself remains constant at any given temperature. This is because K represents the ratio of the equilibrium concentrations of the products to the reactants, raised to the power of their stoichiometric coefficients. The actual concentrations may change with temperature, but the ratio of the concentrations will still yield the same constant value for K.
In summary, while an increase in temperature affects the equilibrium constant expression by modifying the concentrations of the reactants and products, it does not alter the numerical value of the equilibrium constant itself, which remains constant at a particular temperature.