Question

Explain the relation between gibbs free energy and equilibrium constant.

Answer 1

A spontaneous reaction has a negative delta G and a large K value. A non-spontaneous reaction has a positive delta G and a small K value. When delta G is equal to zero and K is around one, the reaction is at equilibrium. ... This relationship allows us to relate the standard free energy change to the equilibrium constant.

Answer 2

Gibbs free energy tells us whether a reaction is spontaneous one or not.

The change of Gibbs energy of a reaction is given by,

∆G°=∆H°-T∆S°

Where ∆G is the change in free energy, ∆H is the change in enthalpy, T is temperature in Kelvin and ∆S is change in entropy.

This equation can be rewritten in terms of free energy and reaction quotient Q.  

∆G =∆G°+RT InQ

The equilibrium constant K also tells about the reaction is spontaneous are not.

At equilibrium Q=k and ∆G=0.

Then,

∆G°=-RT InK