Consider the decomposition of hydrogen bromide to form hydrogen and gaseous bromine, Br2(g): HBr(g) 1/2 H2(g) + 1/2 Br2(g) H = 72.5 kJ (a) What is the enthalpy change for the reverse reaction? Hreverse = kJ/mol. (b) Balance the forward reaction with whole-number coefficients. What is H for the reaction represented by this equation? H = kJ/mol.