RELATIONSHIP BETWEEN EQUILIBRIUM CONSTANT K, REACTION QUOTIENT Q AND GIBBS ENERGY G.

A mathematical expression of thermodynamic view of equilibrium can be described by tine equation.

ΔG = ΔGº + RT InQ

Where, ΔGº is standard Gibbs energy.

At equilibrium, ΔG = 0 and Q = Kc, so the equation becomes,

0 = ΔGº + RT In Kc

Or, ΔGº = - RT InKc

On changing the base we get ΔGº = -2.303RT log Kc

We know that for a spontaneous process ΔG should be negative. So the value of Kc should be positive.