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