Gibbs free energy — will a reaction go?

ΔG = ΔH − T·ΔS decides spontaneity: a reaction proceeds on its own only when ΔG < 0. Sealed in-domain: ΔH = −100 kJ/mol, ΔS = 200 J/mol·K at 300 K gives ΔG = −160 kJ/mol — spontaneous (https://narrowhighway.com/s/54db514fbdd51c90cad455bc773f8152da3b3eb6a53119da6ddb670c9464e23b). It is a tug-of-war: enthalpy (ΔH, the energy released) pulls one way, entropy (ΔS, the disorder gained) the other, and TEMPERATURE sets the referee — which is why some reactions run only when heated. This is the second law of thermodynamics doing chemistry, the same entropy arrow that pointed the Fokker–Planck fluid toward equilibrium. Rate is a separate, empirical question (a spontaneous reaction can still be slow — diamond 'wants' to become graphite).