For a certain reaction, $\Delta \mathrm{H}^{\circ}=219 \mathrm{~kJ}$ and $\Delta \mathrm{S}^{\circ}=-21 \mathrm{JK}^{-1}$. Find the value of $\Delta \mathrm{G}^{\circ}$.

Calculate the work done in following reaction.

$$ \begin{aligned} & \mathrm{C}_2 \mathrm{H}_{4(\mathrm{~g})}+\mathrm{HCl}_{(\mathrm{g})} \longrightarrow \mathrm{C}_2 \mathrm{H}_5 \mathrm{Cl}_{(\mathrm{g})} \text { at } 27^{\circ} \mathrm{C} . \\ & \left(\mathrm{R}=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right) \end{aligned} $$

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.

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