Question

Standard heats of formation for $C{Cl}_4,H_{2}O,{CO}_2$ and $HCl$ at $298K$ are $-25.5,-57.8,-94.1$ and $-22.1kJ/mol$ respectively.
For the reaction, what will be $\Delta H$?
$C{Cl}_4+2H_{2}O\to {CO}_2+4HCl$

• A. $36.4kJ$
• B. $20.7kJ$
• C. $-20.7kJ$
• D. $-41.4kJ$

Answer 1

The correct option is D $-41.4kJ$

For the given reaction,
$CC{l}_4+2H_{2}O\to C{O}_2+4HCl$
$\Delta H=\Delta H_{f\left(C{O}_2\right)}+$ $4\times$ $\Delta H_{f\left(HCl\right)}$ - $\Delta H_{f\left(CC{l}_4\right)}$ - $2\times$ $\Delta H_{f\left(H_{2}O\right)}$
=> $\Delta H=-94.1+4\times (-22.1)-(-25.5)-2\times (-57.8)=-41.4KJ$
Hence, answer is option $D$.