For water \( \Delta_{\text{vap}}H = 41 \, \text{kJ mol}^{-1} \) at \( 373 \, \text{K} \) and \( 1 \, \text{bar} \) pressure. Assuming that water vapour is an ideal gas that occupies a much larger volume than liquid water, the internal energy change during evaporation of water is ________ \( \text{kJ mol}^{-1} \).
[Use : \( R = 8.3 \, \text{J mol}^{-1} \, \text{K}^{-1} \).]