When 1 gm of water changes from liquid to vapour phase at constant pressure of 1 atmosphre, the volume increases from 1cc to 1671cc. The heat of vaporisation at his pressure is 540 cal/gm. Increase in internal energy of water is (1 atmosphre =1.01x `10^(6)` dyne/`cm^(2)`)

Options

A. `2099 J`
B. `3000 J`
C. `992 j`
D. `2122 j`

Answer

A

Explanation

`W=P(dV) = 0.01xx10^(5)(1671-1)xx10^(-6)=167J`
`Q = DeltaU+W`
or, `Delta U = Q-W = mL-167 = 540 xx 4.2 -167`
`=2099J`.