01ΔG = ΔH − TΔS
ΔG < 0 → thermodynamically favorable. The four sign cases: −ΔH/+ΔS always favorable; +ΔH/−ΔS never; −ΔH/−ΔS favorable at low T; +ΔH/+ΔS favorable at high T.
Crossover temperature: T = ΔH/ΔS.
02Notebook box
ΔG° = Σ ΔG°f(products) − Σ ΔG°f(reactants) also works.
Worked example: ΔH = +50 kJ, ΔS = +0.200 kJ/K → favorable above T = 250 K.