Question

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

Answer 1

If we know the equilibrium constant, `K_(eq)`, for a chemical change we can calculate the standard state free energy change, `Delta G^@`.

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_(eq)`, for a chemical change, we can calculate the standard state free energy change, `DeltaG^@`, for the reaction using the equation:

`Delta G^@ = -RTlnK_(eq)`

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

The equilibrium composition of the mixture is determined by `DeltaG^@` which also defines the equilibrium constant K.
http://www.chem1.com/acad/webtext/thermeq/TE5.html