Q53. $\Delta _ { \text {vap } } \mathrm { H } ^ { \ominus }$ for water is $+ 40.79 \mathrm {~kJ} \mathrm {~mol} ^ { - 1 }$ at 1 bar and $100 ^ { \circ } \mathrm { C }$. Change in internal energy for this vapourisation under same condition is $\mathrm { kJmol } ^ { - 1 }$. (Integer answer) (Given $\mathrm { R } = 8.3 \mathrm { JK } ^ { - 1 } \mathrm {~mol} ^ { - 1 }$ )