The bond enthalpy of H2O and OH are 502 KJ mol-1 and 427 KKJ mol-1. Then what is the average bond enthalpy?

The bond enthalpy of H2O and OH are 502 KJ mol-1 and 427 KKJ mol-1. Then what is the average bond enthalpy? Correct Answer 464.5 KJ mol-1

We know that H2O(g) → H(g) + OH(g); ΔH1 = 502 kJ mol-1 and OH(g) → H(g) + O(g); ΔH2 = 427 kJ mol-1. So the average bond enthalpy is given by their mean that is 427 + 502/2 = 464.5 KJ mol-1. This method is used for polyatomic molecules like water.
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