Calculating the Heat of Reaction from Heats of formation Use the following information to find ^Hf of methanol [CH3OH(l)]. CH3OH(l) + 3/2 O2(g) CO2(g) + 2 H2O(g) (heat)H°comb = -638.5 (heat)H°f of CO2(g) = -393.5 kJ/mol (heat)H°f of H2O(g) = -241.8 kJ/mol