Question

Why gibbs free energy is negative for a spontaneous process?

Answer 1

The sign of ΔG will change from positive to negative (or vice versa) where T = ΔH/ΔS. In cases where ΔG is: negative, the process isspontaneous and may proceed in the forward direction as written. positive, the process is non-spontaneous as written, but it may proceed spontaneously in the reverse direction

Answer 2

Spontaneous processes have a negative free energy change, DG is negative or less than zero. The system releases energy to its surroundings as the process occurs. This kind of change is an exergonic process, delta G = -. The size of the free energy change indicates the "driving force" behind the reaction.