One mole of a perfect gas expands isothermally and reversibly from $10 \mathrm{dm}^3$ to $20 \mathrm{dm}^3$ at 300 K . Find $\Delta \mathrm{U}, \mathrm{q}$ and work done respectively in the process. $\left(\mathrm{R}=8.3 \times 10^{-3} \mathrm{~kJ} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right)$

Calculate heat of formation of $\mathrm{SO}_2$ from following equations.

$$ \begin{aligned} & \mathrm{S}+\frac{3}{2} \mathrm{O}_2 \longrightarrow \mathrm{SO}_3, \Delta \mathrm{H}=-2 \mathrm{xkJ} \\ & \mathrm{SO}_2+\frac{1}{2} \mathrm{O}_2 \longrightarrow \mathrm{SO}_3, \Delta \mathrm{H}=-\mathrm{ykJ} \end{aligned} $$

Which of the following symbols represents heat of reaction at constant pressure?

The entropy of vaporisation of benzene is $85 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$. When 117 g of benzene vaporises at its boiling point, what is entropy change of surrounding if process is at equilibrium?