Calculate the enthalpy of the reaction 2NO(g)+ O 2 (g)→2N O 2 (g) given the following reactions and enthalpies of formation: 1 2 N 2 (g)+ O 2 (g)→N O 2 (g), Δ H ∘ A =33.2 kJ 1 2 N 2 (g)+ 1 2 O 2 (g)→NO(g), Δ H ∘ B =90.2 kJ