The enthalpy of combustion of C, $\text{H}_2$, and $\text{CH}_4$ are $-390$, $-285$ and $-890$ kJ/mol. Find the enthalpy of formation of methane.

Calculate the change in internal energy if an ideal gas expands from $0.5\ \text{dm}^3$ to $3.5\ \text{dm}^3$ at constant pressure 2 bar by absorbing 1800 J heat energy.

Which of the following processes exhibits the decrease in internal energy of a system?

If $2$ mole of an ideal gas expand isothermally and reversibly at $27^\circ$C from 1 $\text{dm}^3$ to $1\ \text{m}^3$ calculate work done? $[R = 8.314\ \text{J K}^{-1}\text{mol}^{-1}]$