The latent heat of vaporisation of water is 2240 J/gm. If the work done in the process of expansion of 1 g of water is 168 J, then increase in internal energy is

Options

A. 2408 J
B. 2072 J
C. 2240 J
D. 1904 J

Answer

B

Explanation

Latent heat of vapourisation of water (L)=2240 J, mass of the water (m)=1 g and work done (dW)=168J.
From first law of thermodynamics , heat supplied in vapourisation ` (dQ)=mL =dU+dW`
or `1 xx 2240=dU+168`
or `dU=2240-168=2072J` (where dU= increase in internal energy )