A thermally insulated vessel contains 150   g of water at 0 ° C . Then the air from the vessel is…

A thermally insulated vessel contains 150 g of water at 0°C . Then the air from the vessel is pumped out adiabatically. A fraction of water turns into ice and the rest evaporates at 0°C itself. The mass of evaporated water will be closest to: (Latent heat of vaporization of water =2.10×106 J kg-1 and Latent heat of Fusion of water =3.36×105 J kg-1 )
  1. 35 g
  2. 20 g
  3. 130 g
  4. 150 g

Solution

Suppose m grams of water evaporate. Then, heat required
ΔQreq=mLv
Mass that converts into ice =150-m
Heat released in the process,
ΔQrel=150-mLf
Now, ΔQrel=ΔQreq
150-mLf=mLv
mLf+Lv=150 Lf
m=150LfLf+Lv
m=20 g

Asked in: JEE Main 2019 (08 Apr Shift 1)

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