Question

Heat of reaction for; $CO\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\to {CO}_2\left(g\right)$ at constant V is $-67.71$ cal ${17}^{o}C$. The heat of reaction at constant P at ${17}^{o}C$:

• A. $-68.0Kcal$
• B. $+68.0Kcal$
• C. $-67.42Kcal$
• D. None of these

Answer 1

The correct option is A $-68.0Kcal$

Heat of reaction at constant pressure$\Rightarrow △H$

Heat of reaction at constant volume $\Rightarrow △U$

$△U=-67.71KCal$

$△H=△U+△nRT$

Again,

$△n=1-(1+\frac{1}{2})=-0.5$

$\Delta H=-67.71+\frac{(-0.5)\left(2\right)\left(290\right)}{1000}$

$=-67.71-0.29$

$=-68.0$ $kCal$