The bond dissociation energies for Cl₂, I₂ and ICl are 242.3, 151 and 211.3 KJ/mol respectively.The enthalpy of the sublimation of iodine is 62.8 kJ/mol. What is the standard enthalpy of formation of ICl_(g) ?

Reaction for formation of Icl_(g) is
$\frac{1}{2}{\mathrm{I}}_{2\left(\mathrm{g}\right)}+\frac{1}{2}{\mathrm{Cl}}_{2\left(\mathrm{g}\right)}\to {\mathrm{ICl}}_{\left(\mathrm{g}\right)};{\mathrm{\Delta H}}_1\dots \dots \to 1$
Get equation for $∆$H₁ interms of bond energy we have to use,
${\mathrm{I}}_{2\left(\mathrm{s}\right)}\to {\mathrm{I}}_{2\left(\mathrm{g}\right)}; \mathrm{\Delta H}\to 2$  subtimation
$\mathrm{eq}.\left(1\right)-\mathrm{eq}\cdot \left(2\right)\times \frac{1}{2}$ gives
$\begin{array}{l}\frac{1}{2}{\mathrm{I}}_{2\left(\mathrm{g}\right)}+\frac{1}{2}{\mathrm{Cl}}_{2\left(\mathrm{g}\right)}\to {\mathrm{ICl}}_{\left(\mathrm{g}\right)}{\mathrm{\Delta H}}_3\\ \therefore {\mathrm{\Delta H}}_3={\mathrm{\Delta H}}_1-\frac{{\mathrm{\Delta H}}_2}{2}\\ =\frac{1}{2}\left(\mathrm{B}\cdot {\mathrm{EofI}}_2\right)+\frac{1}{2}\left({\mathrm{B}}_{\mathrm{E}}\text{ EofCl }2\right)-\mathrm{B}\cdot \mathrm{CofICL}\\ {\mathrm{\Delta H}}_1-\frac{62.8}{2}=\frac{1}{2}(242.3)+\frac{1}{2}\left(151\right)-211.3\\ \therefore {\mathrm{\Delta H}}_1=16.75\mathrm{kJ}=4019\mathrm{cal}\end{array}$