Question

Consider the reaction at $300$K.
$H_2\left(g\right)+C{l}_2\left(g\right)\to 2HCl\left(g\right);$ $\Delta H^o=-185$kJ
If $2$ mole of $H_2$ completely react with $2$ mole of $C{l}_2$ to form HCl. What is $\Delta U^o$ for the reaction?

• A. $0$
• B. $-185$ kJ
• C. $370$ kJ
• D. None of these

Answer 1

The correct option is A $0$

$2$ mol $H_2$ and $2$ mol $C{l}_2$ react as follows-

$2H_2+2C{l}_2\to 2HCl$

Enthalpy of reaction change when we multiply or divide the reaction with any number.

So enthalpy for the reaction$=-185\times 2=-370KJ$