Question

$C+O_2\to C{O}_2;\Delta H=-94Kcal;$
$CO+\frac{1}{2}{O}_2\to C{O}_2;\Delta H=-67.7Kcal$
On the basis of the above data, the heat of formation of $CO$ is:

• A. -26.3 K.cals
• B. +26.3 K.cals
• C. +52.6 K.cals
• D. +13.2 K.cals

Answer 1

The correct option is A -26.3 K.cals

(i) $C+O_2\to C{O}_2,\Delta H=-94$ Kcal
$CO+\frac{1}{2}{O}_2\to C{O}_2,\Delta H=-67.7$ Kcal
(ii) $C{O}_2\to CO+\frac{1}{2}{O}_2,\Delta H=67.7$ Kcal
Adding (i) and (ii), we get
$C+\frac{1}{2}{O}_2\to CO$
$=-94+67.7$ Kcal

$\Delta H=-26.3$ Kcal

Option A is correct.