Thermodynamics Question 295
Question: 1 gm of water at a pressure of $ 1.01\times 10^{5} $ Pa is converted into steam without any change of temperature. The volume of 1 g of steam is 1671 cc and the latent heat of evaporation is 540 cal. The change in internal energy due to evaporation of 1 gm of water is
Options:
A) $ \approx 167cal $
B) $ \approx 500cal $
C) 540 cal
D) 58 cal
Show Answer
Answer:
Correct Answer: B
Solution:
[b] $ dW=P\Delta V=1.01\times 10^{5}[ 1671-1 ]\times 10-6Joule $
$ =\frac{1.01\times 167}{4.2}cal.=40\text{cal}\text{. nearly} $
$ \Delta Q=mL=1\times 540. $
$ \Delta Q=\Delta W+\Delta U $
$ \text{or }\Delta U=540-40=500\text{ cal}\text{. } $
