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Internal energy change for vaporising water at 100 C and 1 bar from its enthalpy of vaporisation

The same question, asked 3 times: 2021 Paper 19*, 26 Jun 2022*, 8 Apr 2024. Every wording below, oldest first.

Try each one first, then open its answer.

  1. Question 1

    2021 Paper 19

    53
    For water Δvap H=41 kJ mol−1\Delta_{\text{vap~}}H = 41\text{ }kJ{\text{ }mol}^{- 1} at 373 K373\text{ }K and 1 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 ____\_\_\_\_ kJmol−1kJmol^{- 1} [Use: R=8.3 J mol−1 K−1R = 8.3\text{ }J{\text{ }mol}^{- 1}{\text{ }K}^{- 1} ]

  2. Question 2

    26 Jun 2022

    144
    A fish swimming in water body when taken out from the water body is covered with a film of water of weight 6 g6\text{ }g. When it is subjected to cooking at 100∘C100^{\circ}C, then the internal energy for vaporization in kJmol−1kJmol^{- 1} is ____\_\_\_\_ [nearest integer] [Assume steam to be an ideal gas. Given ΔvapH⊖\Delta_{vap}H^{\ominus} for water at 373 K373\text{ }K and 1 bar is 41.1 kJ mol−141.1\text{ }kJ{\text{ }mol}^{- 1}; R=R = 8.31JK−1 mol−18.31JK^{- 1}{\text{ }mol}^{- 1} ]

  3. Question 3

    8 Apr 2024

    141
    Δvap H⊖\Delta_{\text{vap~}}H^{\ominus} for water is +40.49 kJ mol−1+ 40.49\text{ }kJ{\text{ }mol}^{- 1} at 1 bar and 100∘C100^{\circ}C. Change in internal energy for this vapourisation under same condition is _______ JJ mol−1mol^{- 1}. (Integer answer) (Given R=8.3JK−1 mol−1R = 8.3JK^{- 1}{\text{ }mol}^{- 1} )