`1gm` water at `100^(@)C` is heated to convert into steam at `100^(@)C` at `1atm`. Find out chage in internal energy of water. It is given that volume of `1gm` water at `100^(@)C = 1c c`, volume of `1gm` steam at `100^(@)C = 167 1 c c`. Latent heat of vaporization `= 540 cal//g`. (Mechanical equivalent of heat `J = 4.2J//cal)`

Explanation

From first law of thermodynamic `DeltaQ=Delta u + Delta W`
`Delta Q = mL =1 xx 540 cal. =540cal.`
`Delta W=P Delta V = (10^(5) (1671-1) xx 10^(-6))/(4.2)`
`= (10^(5) (1670) xx10^(-6))/(4.2)=40 ca.`
`Delta U =540 -40=500` cal.