What is the work done when a gas is compressed from 2.5 $$\times$$ 10$$^{-2}$$ m$$^3$$ to 1.3 $$\times$$ 10$$^{-2}$$ m$$^3$$ at constant external pressure of 4.05 bar?

Calculate heat of formation of $$\mathrm{HCl}$$ gas from following reaction.

$$\mathrm{H}_{2(\mathrm{~g})}+\mathrm{Cl}_{2(\mathrm{~g})} \rightarrow 2 \mathrm{HCl}_{(\mathrm{g})} ; \Delta \mathrm{H}=-194 \mathrm{~kJ}$$

Calculate difference between $$\Delta \mathrm{H}$$ and $$\Delta \mathrm{U}$$ for following reaction at $$25^{\circ} \mathrm{C}$$ ?

$$\mathrm{C}_2 \mathrm{H}_{6(\mathrm{~g})}+3.5 \mathrm{O}_2 \rightarrow 2 \mathrm{CO}_{2(\mathrm{~g})}+3 \mathrm{H}_2 \mathrm{O}_{(l)}\left(\mathrm{R}=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right)$$

The change in internal energy of a system depends upon