Standard free energy change and equilibrium constant

The standard free energy change is defined as the free energy change for a process at 298 K and 1 atmospheric pressure in which the reactants in their standard states are converted to the products in their standard states. Like the standard enthalpy of formation of an element, the standard free energy of formation of an element in its standard state is assumed to be zero. Thus,

Standard free energy change and equilibrium constant

The standard free energy change, DG^o is related to the equilibrium constant K by the relation,

DG^o = - RT ln K

or DG^o = - 2.303 RT log K ('.' ln X = 2.303 log X)

This relation helps us to calculate the value of DG^o if K is known or vice-versa.