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To determine the enthalpy of a reaction using bond energy

DH^o_(reaction) =SH_{(bonds broken)} - SH_{(bonds formed)} 

_{Break the reactants and make the products. Each bond must be accounted for.}

Calculate the H for the following reaction in the gas phase.  

DH	=SH(bonds broken) - SH(bonds formed)
DH	=(2(N-H) + (N=N) + 2(O-H)) - (2(N-H) + (N-O) + (O-H) + 3(N-H))
DH	=(2(391)+418)+2(463)) - (2(391) + 201 + 463 + 3(391))
DH	=2126-2619= -493kJ

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