Δ_vap H^ for water is +40.79 kJ mol^-1 at 1 bar and 100^° C. Change in internal energy for this vapourisation under same condition is ____ kJ mol^-1.…

$\displaystyle \Delta_{\text {vap }} \mathrm{H}^{\ominus}$ for water is $\displaystyle +40.79 \mathrm{~kJ} \mathrm{~mol}^{-1}$ at $\displaystyle 1$ bar and $\displaystyle 100{ }^{\circ} \mathrm{C}$. Change in internal energy for this vapourisation under same condition is $\displaystyle \_\_\_\_$ $\displaystyle \mathrm{kJ} \mathrm{mol}^{-1}$. (Integer answer) (Given $\displaystyle \mathrm{R}=8.3 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}$ )