1 g of water at 100^(@)C is converted into steam at the same temperature. If the volume of steam is 1671 cc find the change in internal energy of the system. Latent heat of steam =2256 J g ^(-1).

1 g of water at 100^(@)C is converted into steam at the same temperatu

1.	1 g of water at 100^(@)C is converted into steam at the same temperature. If the volume of steam is 1671 cc find the change in internal energy of the system. Latent heat of steam =2256 J g ^(-1).
Answer» Solution :According to first law of thermodynamics `dQ = dU + PdV` `mL = dU + P( VS - Vw)` Mass of water `= m = 1 g = 10 ^(-3) kg ` Latent heat of STEAM `= L = 2256 Jg ^(-1) = 2256 XX 10 ^(3) Jkg ^(-1)` Changle in internal energy ` = dU = ?` Atmospheric pressure ` = P = 1. 013 xx 10^(5) Nm ^(-2)` Volume of steam `V_(s) = 1671 c c = 1671 xx 10 ^(-6) m ^(3)` Volume fo water `V_(w) = ( "mass")/("density") = (10 ^(-3))/( 10 ^(3)) = 10 ^(-6) m ^(3)` `dU = mL - P (Vs - vW)` `= 10^(-3) xx 2256 xx 10 ^(3) - 1. 013 xx 10 ^(5) (1617 xx 10 ^(-5) - 10 ^(-6))` `= 1156 - 1.013 xx 10 ^(5) xx 10 ^(-6) xx 1670` `= 2256 - 169.171 = 2086 . 829 J`