The chemical potential of the component i in a system is defined as the change in the Gibbs free energy with change in the mole of component i when temperature (T) and pressure (P) and the mole of other components are kept constant.
The condition of equilibrium of a chemical reaction is that the free energy must be minimum
Kc , the equilibrium constant is a function only of temperature. It is a dimensionless quantity, and is the ratio of the molarities of the products and reactants.
For the general reaction : RT ln Kp= -delta G (zero)