A look into what Gibbs energy is and how it can be used to show spontaneity:
If you’ve studied A-Level chemistry, you’ve heard of the Gibbs free energy equation.
ΔG = ΔH – TΔS
You’ve used this equation to determine whether a reaction is spontaneous, non-spontaneous or at equilibrium, with reactions that have a negative ΔG being spontaneous, those that have a positive ΔG being non-spontaneous and those with ΔG = 0 being at equilibrium.
Firstly, what does it mean. Well, as suggested by the name, Gibbs free energy shows the energy available in a chemical reaction for work to be done. That’s why the units of Gibbs free energy are J/mol or kJ/mol.