The standard enthalpy of combustion of C (graphite). $\mathrm{H}_2(g)$ and $\mathrm{CH}_3 \mathrm{OH}(l)$ respectively are $-393,-286$ and $-726 \mathrm{~kJ} \mathrm{~mol}^{-1}$. What is the standard enthalpy of formation of methanol?

At 61 K , one mole of an ideal gas of 1.0 L volume expands isothermally and reversibly to a final volume of 10.0 L . What is the work done in the expansion?

The standard enthalpy of formation $\left(\Delta_f H^{\varphi}\right)$ of ammonia is $-46.2 \mathrm{~kJ} \mathrm{~mol}^{-1}$, What is the $\Delta_{,} H^{\ominus}$ of the following reaction? $$ \mathrm{N}_2(g)+3 \mathrm{H}_2(g) \longrightarrow 2 \mathrm{NH}_3(g) $$

If 2.5 moles of an ideal gas at a certain temperature are allowed to expand isothermally and reversibly from an initial volume of $2 \mathrm{dm}^3$ to $20 \mathrm{dm}^3$, the work done by the gas is -16.5 kJ . The temperature (in K ) of the gas is (Round off to the nearest value) ( $R=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$ )