Question

Bond dissociation enthalpies of $H_{2\left(g\right)},C{l}_{2}andHC{l}_{\left(g\right)}$ are 104, 58 and 103 kcal respectively. The enthalpy of formation of HCl is

• A. - 44 kcal
• B. - 88 kcal
• C. - 22 kcal
• D. - 11 kcal

Answer 1

The correct option is A - 44 kcal

$H_{2\left(g\right)}+C{l}_{2\left(g\right)}\to 2HC{l}_{\left(g\right)}$
$\sum \left(BEofreactants\right)-\sum \left(BEofproducts\right)=\Delta H_r$
$=104+58-2\times 103$