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JEE Main 202126 AugustEvening Shift
Exam
JEE Main
Year
2021
Date
26 August
Shift
Evening Shift
Subject
Chemistry
Chapter
Structure of Atom

JEE Main 2021 · 26 August · Evening Shift · Chemistry · Structure of Atom

For water Δ _ vap H = 41kJ mol ^ - 1 at 373K and 1 bar pressure....

For water ΔvapH=41kJmol−1{\Delta}_{vap}H = 41kJ{mol}^{- 1} at 373K373K 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−1)( {kJmol}^{- 1} ):
[ Use \left: R = 8 . 3J{mol}^{- 1}{K}^{- 1}\right]

Correct answer

38

Step-by-step solution

H2O(l)⇌H2O(g);ΔHvap.=41kJ/mol{H}_{2}O ( l ) ⇌ {H}_{2}O ( g ) ; {\Delta H}_{vap .} = 41kJ / mol

ΔH=ΔU+ΔngRT\Delta H = \Delta U + {\Delta n}_{g}RT

41=ΔU+(1)8.31000×37341 = \Delta U + ( 1 ) \dfrac{8 . 3}{1000} \times 373

\DeltaU=41−3.0959\DeltaU = 41 - 3 . 0959

ΔU=37.9kJ/mol≃38kJ/mol\Delta U = 37 . 9kJ / mol ≃ 38kJ / mol

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