What is meant by the term average

Similar bonds in a molecule do not have the same bond enthalpies. Mainly the term average bond enthalpy is used in polyatomic molecules. It is obtained by dividing

bond dissociation enthalpy by the number of bonds broken. The bond enthalpy of OH bond is different in ethanol and water because of the difference in

electronegativity of hydrogen and carbon. As electronegativity differs in hydrogen and oxygen is higher than that in carbon and oxygen, so the O-H bond in water has

more bond enthalpy than in ethanol.