As a reaction undergoes a change from its initial to final state the change in its free energy is termed as of the system.
It is also the energy associated with a chemical reaction that can be used to do work.
The change in the enthalpy of the system minus the product of the temperature (Kelvin) and entropy variation () of the system denotes the Change in free energy of the system. which is given by;
For a reaction to be spontaneous, the change in Gibbs free energy should be negative.
Therefore, we can calculate Change in free energy by using the formula as: