One mole of an ideal gas at $300 \mathrm{~K}$ is expanded isothermally from an initial volume of 1 litre to 10 litres. The $\Delta \mathrm{E}$ for this process is $\left(\mathrm{R}=2\right.$ cal $\left.\mathrm{mol}^{-1} \mathrm{~K}^{-1}\right)$