The bond dissociation enthalpy of gaseous $H_2, Cl_2$ and $HCl$ are $435, 243$ and $431\; kJ mol^{-1},$ respectively. Calculate the enthalpy of formation of HCl gas.

Question

$\begin{array}{1 1} (a)\; -92\; kJ \\ (b) \;-102 \;kJ \\ (c) \;-82\; kJ \\ (d) \;92 \;kJ \end{array}$