Calculate the bond enthalpy of OH bond in water.

Explanation

(i) In the case of polyatomic molecules with two or more same bond types. the arithmetic mean of the bond energy value of the same type of bonds is considered as average bond enthalpy.
(ii) For e.g., in water, there are two OH bonds present and the energy needed to break them are not same.
(iii) `H_(2)O (g) rarr H(g) +OH" "DeltaH_(1)= 502 " kJ mol"^(-1)`
`OH (g) rarr H (g) + O(g) " " DeltaH = 427 " kJ mol"`
The average bond enthalpy of OH bond in water `=(502+427)/(2)=464.5 " kj mol"^(-1)`