Question

Calculate the enthalpy of the reaction,
$H_2\left(g\right)+{Cl}_2\left(g\right)⟶2HCl\left(g\right)$
given that, bond energies of $H-H,Cl-Cl$ and $H-Cl$ are $436,243$ and $432$ $kJ{mol}^{-1}$.

• A. $-185kJ{mol}^{-1}$
• B. $-285kJ{mol}^{-1}$
• C. $-385kJ{mol}^{-1}$
• D. None of these

Answer 1

The correct option is A $-185kJ{mol}^{-1}$

Enthalpy of reaction = energy of product - energy of reactant

Enthalpy of reaction = $(436+243)-2\ast 4432=-185KJmo{l}^{-1}$