Calculate the standard reaction enthalpy for the reaction NO2(g) → NO(g) + O(g) Given: O2(g) → 2 O(g) ∆H◦ = +498.4 kJ/mol NO(g) + O3(g) → NO2(g) + O2(g) ∆H◦ = −200 kJ/mol 3O2(g) → 2 O3(g) ∆H◦ = +285.4 kJ/mol