Answer is: - delta G. The change in Gibbs free energy (ΔG), at constant temperature and pressure, is: ΔG=ΔH−TΔS. ΔH is the change in enthalpy. ΔS is change in entropy. T is temperature of the system. When ΔG is negative, a reaction (occurs without the addition of external energy) will be spontaneous (exergonic).
