Final answer:
The only factor that can change the equilibrium constant Kc is temperature.
Step-by-step explanation:
The only factor that can change the equilibrium constant Kc is temperature. The value of the equilibrium constant is determined by experiment and is truly constant, but it does depend on the temperature of the reaction. If the temperature changes, the equilibrium constant will be altered as it is based on the rates of forward and reverse reactions, which are affected by temperature. Concentrations and other factors do not change the equilibrium constant.