Question

Formula to calculate bond disassociate energy?

Answer 1

Bond Dissociation Energy Equation
Evaluation of bond dissociation energy is a typical application of thermochemical information. The information on bond dissociation energy may indicate which bond is more likely to break in a molecule and can be used to estimate the temperature range. The reaction of bond dissociation can be written as follows.
A-B →→ A^. + B^.

For the above equation the differences between enthalpy and energy can be written as
ΔH - ΔE = ∑(pV)_fragments - (pV)_molecule = (Δn)RT
There is variation in bond energy and bond enthalpy, true bond energy should be taken at 0K and not at 298.3K. However these differences are very small compared to the value of the bond dissociation energy and in general the bond dissociation energy is taken as equal to the negative value for the enthalpy of formation of the bond. The enthalpy of bond dissociation is given by the expression.
ΔH^o_f(A-B) = ΔH^o_f(A^o) + ΔH^o_f(B^o) - ΔΔH^o_f(AB)