Thermodynamics Question 179

Question: Unit mass of a liquid with volume $ V _{1} $ is completely changed into a gas of volume $ V _{2} $ at a constant external pressure P and temperature T. If the latent heat of evaporation for the given mass is L, then the increase in the internal energy of the system is

[Roorkee 1999]

Options:

A) Zero

B) $ P(V _{2}-V _{1}) $

C) $ L-P(V _{2}-V _{1}) $

D) L

Show Answer

Answer:

Correct Answer: C

Solution:

$ \Delta Q=\Delta V+P\Delta V $

Therefore mL = DU + P(V2 - V1)

Therefore DU = L - P (V2 - V1) ($ \because $ m = 1)



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