1. The problem statement, all variables and given/known data Given the data in the table below, ΔH°rxn for the reaction 4NH3 (g) + 5O2 (g) → 4NO (g) + 6H2O (l) is ________ kJ. Substance ΔH∘f(kJ/mol) H2O (l) -286 NO (g) 90 NO2 (g) 34 HNO3 (aq) -207 NH3 (g) -46 2. Relevant equations ΔH°rxn = ΔH°products - ΔH°reactants 3. The attempt at a solution ΔH°rxn = [(4x90)+(6x-286)] - [(4x-46)+(X)] ΔH°rxn = (-1356) - (-184+X) ΔH°rxn = -1356 + 184 - X ΔH°rxn = -1172 + X At first I selected, D.) The ΔH°f of O2 (g) is needed for the calculation. However, apparently the answer is -1172, but I have no idea why. How can -1172 be the answer here? And why do they give me the enthalpy of formation for NO2 and HNO3 if neither of those compounds are in my reaction?