When 1g of the water at 100^(@)C is converted into stream at 100^(@)C,. it occupiesa volume of 1671 cc at normal atomospheric pressure. Find the increase in internal energy of the molecules of steam.

When 1g of the water at 100^(@)C is converted into stream at 100^(@)C,

1.	When 1g of the water at 100^(@)C is converted into stream at 100^(@)C,. it occupiesa volume of 1671 cc at normal atomospheric pressure. Find the increase in internal energy of the molecules of steam.
Answer» SOLUTION :1 atomosphere `=1.013 xx 10^(5)Nm^(-2)`, volume of 1 GM of water, `V_(1) = 1 cc = 10^(-6) m^(3)`, Volume of steam `=1671 cc = 1671 xx 10^(-6)m^(3)` Externalwork DONE `dW = P(V_(2)-V_(1))` `=1.013 xx 10^(5) (1671 xx10^(-6) - 1xx10^(-6))` `=1.013 xx 167 =169.2 J`. Specific latent hat of vaporisation of steam = 540 cal/g. So, heat supplied to convert 1g of water into steam, `DeltaQ=540 xx 4.2J=2268J` By firstlaw of thermodynamics `DeltaU= DeltaQ -DeltaW = 2268 - 169.2 = 2098.8J`