Question

$\Delta H$ for the reaction, $OF_2 + H_2O \to O_2 + 2HF$
$(B.E.$ of $O — F$, $O — H$, $H — F$ and $O = O$ are $44$, $111$, $135$ and $119\, kcal\, mol^{-1}$ respectively)

• A. $- 222\, kcal$
• B. $- 88\, kcal$
• C. $- 111\, kcal$
• D. $- 79\, kcal$

Answer 1

Answer: (D)

$\Delta H = \Sigma\,B.E._{R} - \Sigma\,B.E._{P}$
$= \left(2 \times 44 + 2 \times 111\right) - \left(119 + 2 \times 135\right)$
$ = - 79 \,kcal$