Sulfur reacts with oxygen to form sulfur dioxide (SO2(g), Delta. Hf = –296.8 kJ/mol) according to the equation below. Upper S (s) plus upper O subscript 2 (g) right arrow upper S upper o subscript 2 (g). What is the enthalpy change for the reaction? 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..