A hot metal piece is cooled rapidly to 25°C, removing 1000 kJ from the metal. Calculate the change of entropy if energy is absorbed by vaporizing liquid nitrogen at 101.3 kPa pressure.
Answer: D
Nitrogen boiling at 101.3 kPa; m = 1Q2 /h(fg) = 1000/198.842 = 5.029 kg
∆S(N2) = ms(fg) = 5.029(2.5708) = 12.929 kJ/K.