Question
$$\Delta H$$ for the reaction, $$O{F_2} + {H_2}O \to {O_2} + 2HF$$ ( $$B.E.$$ of $$O - F,O - H,H - F$$ and $$O = O$$ are $$44,111,135$$ and $$119\,kcal\,mo{l^{ - 1}}$$ respectively ) is
A.
$$- 222\,kcal$$
B.
$$- 88\,kcal$$
C.
$$- 111\,kcal$$
D.
$$- 79\,kcal$$
Answer :
$$- 79\,kcal$$
Solution :
$$\eqalign{
& \Delta H = \sum {B.E{._R}} - \sum {B.E{._P}} \cr
& \,\,\,\,\,\,\,\,\,\,\, = \left( {2 \times 44 + 2 \times 111} \right) - \left( {119 + 2 \times 135} \right) \cr
& \,\,\,\,\,\,\,\,\,\,\, = - 79\,kcal \cr} $$