Ammonia, NH3 (Delta. Hf = –46.2 kJ), reacts with oxygen to produce water (Delta. Hf = –241.8 kJ) and nitric oxide, NO (Delta. Hf = 91.3 kJ), in the following reaction: 4 upper N upper H subscript 3 (g) plus 5 upper O subscript 2 (g) right arrow 6 upper H subscript 2 upper O (g) plus 4 upper N upper O (g). What is the enthalpy change for this 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..