Question

Given that $\Delta H_{f}( H )=218 \,kJ / mol$, express the $H - H$ bond energy in $kcal / mol$.

• A. 52.15
• B. 911
• C. 104
• D. 52153

Answer 1

Answer: (C)

Given : Given : $\Delta H f( H )=218\, kJ / mol$
i.e., $\frac{1}{2} H_{2} \rightarrow H: \,\,\,\,\Delta H=218 \,kJ / mol$
or $H_{2} \rightarrow 2 H: \,\,\,\,\Delta H=436 \,kJ / mol$
$=\frac{436}{4.18}=104.3 \,kcal / mol$
Thus, $104.3 \,kcal/mol$ energy is absorbed for breaking one mole of $H - H$ bonds. Hence, $H-H$ bond energy is $104.3 \,kcal / mol$.