# How is K_(eq) related to DeltaG^@?

Aug 12, 2017

If we know the equilibrium constant, ${K}_{e q}$, for a chemical change we can calculate the standard state free energy change, $\Delta {G}^{\circ}$.

#### Explanation:

The "free energy" change for a reaction may determine whether it will be spontaneous or not, but "equilibrium" is just the final state of a system. The equations may be solved either way, depending on the available data (equilibrium concentrations or energy change).

If we know the equilibrium constant, ${K}_{e q}$, for a chemical change, we can calculate the standard state free energy change, $\Delta {G}^{\circ}$, for the reaction using the equation:

$\Delta {G}^{\circ} = - R T \ln {K}_{e q}$

http://www.chem.purdue.edu/gchelp/howtosolveit/Thermodynamics/FreeEnergyChange.html

The equilibrium composition of the mixture is determined by $\Delta {G}^{\circ}$ which also defines the equilibrium constant K.