Nitrogen gas when combined with hydrogen gas forms ammonia gas according to the following equation N2(g) + 3H2(g) = 2NH3(g). Delta H(rxn)=-56 kJ. The delta H(rxn) was determined using Hess's Law and the following three related reactions:
2NH3(g) + 4H2O(l) = 2NO2(g) + 7H2(g) delta H=-68kJ
2NO2(g) = N2(g) + 2O2 (g) delta H= ?
H2O(l) = H2(g) + (1/2)O2(g) delta H = -21kJ
Determine the unknown delta H.