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 evap

Question

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 ____ kJ mol − 1 [Use : R = 8.3 J mol − 1 K − 1 ]

TestHub · Accepted Answer

Given equation is H 2 ​ O ( ℓ ) ⟶ H 2 ​ O ( g ) : Δ H = 41 mol kJ ​ ⇒ From the relation : Δ H = Δ U + Δ n g ​ RT ⇒ 41 mol kJ ​ = Δ U + ( 1 ) × 1000 8.3 ​ × 373 ⇒ Δ U = 41 − 3.0959 = 38 kJ / mol

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