Question

Calculate the enthalpy for the following reaction: N2 + O2 → 2 NO given the following bond dissociation energies: N2 = 226 kcal/mol, O2 = 199 kcal/mol and NO = 145 kcal/mol.

Answer 1

ok so for NO to form you need to break N2 and O2 bonds which is endothermic process and then forming of NO is exothermic so it goes like this:
226 + 199 - (2 * 145) = ???
positive values are for endothermic processes and negative for exothermic...
got it?