How to calculate equilibrium constant from Gibbs free energy?

First, let’s describe the chemical reaction which we want to solve for the equilibrium constant. We know that constant pressure and temperature are two of the three conditions necessary for thermodynamic equilibrium to occur. The third condition is that the system must have the same number of particles present before and after the reaction occurs. If you are working with chemical reactions, the particles are the atoms making up the products and reactants, and the total number of atoms equals the sum of the products and reactants.

How to calculate equilibrium constant from Gibbs free energy change?

The answer to this question is found inside the Gibbs free energy function equation. The equilibrium constant is the ratio of the product of the forward reaction rate constant and the product of the reaction’s standard Gibbs free energy change to the product of the backward reaction rate constant and the reaction’s standard Gibbs free energy change (see derivation below).

How to calculate Gibbs free energy from equilibrium constant?

We could use the fact that the Gibbs free energy is given as a negative value of the natural logarithm of the equilibrium constant. We could also express the natural logarotm of the equilibrium constant as the natural logarotm of the forward reaction rate (kf) divided by the natural logarotm of the backward reaction rate (kb).

How to calculate equilibrium constant from Gibbs free energy and entropy?

The Gibbs free energy includes the enthalpy and entropy contributions. The relationship between the Gibbs free energy, entropy, and equilibrium constant is:

How to calculate Gibbs free energy change from equilibrium constant?

Gibbs free energy is the sum of enthalpy change and entropy change. If you have only one reaction at constant temperature and pressure, you can determine the Gibbs free energy change from the equilibrium constant. Since the entropy change is the logarbin of the reaction quotient, you can use the logarithm of the reaction quotient to determine the Gibbs free energy change: