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JEE Main202126 Aug 2021Evening ShiftChemistryStructure of AtomActual

For water Δ vap   H = 41   kJ   mol - 1 at 373   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 - 1 ) : [ Use : R = 8 . 3   J   mol - 1   K - 1

Correct answer

38

Step-by-step solution

H 2 O ( l ) ⇌ H 2 O ( g ) ;    ΔH vap .  = 41   kJ / mol ΔH = ΔU + Δn g RT 41 = ΔU + ( 1 ) 8 . 3 1000 × 373 Δ U = 41 - 3 . 0959 ΔU = 37 . 9   kJ / mol   ≃   38   kJ / mol

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