Chemistry - Thermochemistry Question with Solution | TestHub

Key IdeaRelationship between change in enthalpy and change in internal energy is given as :
$\Delta H=\Delta U+\Delta n_{g}RT$
In the given options,
$\left(\mathrm{A}\right)$$\begin{array}{c}2H_2{O}_2\left(l\right)\to 2H_{2}O\left(l\right)+O_2\left(g\right)\Delta n_g=1\\ \therefore \Delta H=\Delta U+RT\end{array}$
$\left(\mathrm{B}\right)$$\begin{array}{c}C\left(s\right)+O_2\left(g\right)\to C{O}_2\left(g\right)\\ \Delta n_g=1-1=0\\ \therefore \Delta H=\Delta U\end{array}$
$\left(\mathrm{C}\right)$$\begin{array}{c}PC{l}_5\left(g\right)\to PC{l}_3\left(g\right)+C{l}_2\left(g\right)\\ \Delta n_{g}RT=2-3=-1\\ \therefore \Delta H=-\Delta U-RT\end{array}$
$\left(\mathrm{D}\right)$$\begin{array}{c}{N}_2\left(g\right)+3H_2\left(g\right)\to 2N{H}_3\left(g\right)\\ \Delta n_{g}RT=2-3=-1\\ \therefore \Delta H=\Delta U-RT\end{array}$