$$\begin{aligned} & \text { If } \mathrm{C}(s)+\mathrm{O}_2(g) \rightarrow \mathrm{CO}_2(g), \Delta H=-X \\ & \mathrm{CO}(g)+\frac{1}{2} \mathrm{O}_2(g) \rightarrow \mathrm{CO}_2(g), \Delta H=-Y \end{aligned}$$ Calculate $\Delta_f H$ for $\mathrm{CO}_{(g)}$ formation

Three moles of an ideal gas are expanded isothermally from a volume of $300 \mathrm{~cm}^3$ to 2.5 L at 300 K against a pressure of 1.9 atm . The work done in joules is

Calculate the difference between heat of combustion of carbon monoxide gas at constant pressure and at constant volume at $27^{\circ} \mathrm{C} ?\left(R=2 \mathrm{cal} \mathrm{K}^{-1} \mathrm{~mol}^{-1}\right)$

For a process, entropy change of a system is expressed as