What happens to the equilibrium constant when the temperature of a reaction is changed?

The equilibrium constant for a chemical reaction is temperature-dependent due to the relationship between thermodynamics and chemical equilibria. Specifically, the equilibrium constant is affected by changes in temperature in accordance with the van 't Hoff equation, which relates the change in the equilibrium constant to the change in temperature and the standard enthalpy change of the reaction.

When the temperature changes, the value of the equilibrium constant varies in a way that depends on whether the reaction is exothermic or endothermic. For an exothermic reaction (where heat is released), increasing the temperature will cause the equilibrium constant to decrease, shifting the reaction toward the reactants. Conversely, for an endothermic reaction (where heat is absorbed), increasing the temperature results in an increase in the equilibrium constant, favoring the formation of products.

Thus, the correct answer accurately reflects that the equilibrium constant changes based on the enthalpy of the reaction, signifying that the nature of the reaction (whether it is exothermic or endothermic) is crucial in determining how the constant will respond to temperature changes. This underscores the importance of thermodynamic principles in chemical equilibrium.