<p>Assuming that water vapours are ideal gas. The change in internal energy&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mfenced><mrow><mo>&#8710;</mo><mi>U</mi></mrow></mfenced></math>&nbsp;when&nbsp; 1 mol of water is vaporised at 1 bar pressure and&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML" class="wrs_chemistry"><msup><mn>100</mn><mo>&#176;</mo></msup></math>C. (Given molar enthalpy of vaporisation&nbsp; at 1 bar and 373 K is 41 kJ&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>m</mi><mi>o</mi><msup><mi>l</mi><mrow><mo>-</mo><mn>1</mn></mrow></msup></math>&nbsp;R = 8.3 J&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>m</mi><mi>o</mi><msup><mi>l</mi><mrow><mo>-</mo><mn>1</mn></mrow></msup><msup><mi>K</mi><mrow><mo>-</mo><mn>1</mn></mrow></msup></math>) will be:</p>