Calculate work done if 1 mole of an ideal gas compressed isothermally and reversibly from 12 $\mathrm{dm}^3$ to $6 \mathrm{dm}^3$ at $300 \mathrm{~K} .\left[\mathrm{R}=8.314 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}\right]$

Identify from following physical transformations that exhibits decrease in entropy.

Calculate the standard enthalpy change of following reaction.

$$ \mathrm{C}_2 \mathrm{H}_{4(\mathrm{~g})}+3 \mathrm{O}_{2(\mathrm{~g})} \longrightarrow 2 \mathrm{CO}_{2(\mathrm{~g})}+2 \mathrm{H}_2 \mathrm{O}_{(l)} $$

If $\Delta_{\mathrm{f}} \mathrm{H}^{\circ}\left(\mathrm{C}_2 \mathrm{H}_4\right)=-52 \mathrm{~kJ} \mathrm{~mol}^{-1}$

$$ \begin{aligned} & \Delta_{\mathrm{f}} \mathrm{H}^{\circ}\left(\mathrm{CO}_2\right)=-390 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \Delta_{\mathrm{f}} \mathrm{H}^{\circ}\left(\mathrm{H}_2 \mathrm{O}\right)=-286 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned} $$

Which from following process involves zero work done?