Butane C4H10 (g),(Hf = –125.7), combusts in the presence of oxygen to form CO2 (g) (Delta. Hf = –393.5 kJ/mol), and H2O(g) (Delta. Hf = –241.82) in the reaction: 2 upper C subscript 4 upper H subscript 10 (g) plus 13 upper O subscript 2 (g) right arrow 8 upper C upper O subscript 2 plus 10 upper H subscript 2 upper O (g). What is the enthalpy of combustion, per mole, of butane? Use Delta H r x n equals the sum of delta H f of all the products minus the sum of delta H f of all the reactants.