7. (5 pts) (a) A 5-liter vessel is completely filled with pure H2O. If the tempe

Question

7. (5 pts) (a) A 5-liter vessel is completely filled with pure H2O. If the temperature of the vessel is 35°C and the pressure is 1.5 bar, how many phases are there and how much of each phase is present? 1__phases % steam %ice -100% % liquid (b) (5 pts) A 20-liter vessel is initially filled with air, and then 1 liter of liquid water is introduced, displacing lter of air. The air and the water come to vapor-liquid equilibriurm The pressure in the vessel is 4.0 bar and the temperature is 813°C. What is the mole fraction of water vapor in the gas phase? 1 iter of air. The air and the water come to vapor-liquid equilibrium. Mole fraction of water0.125

Explanation / Answer

(a) From the saturated steam table at P = 1.5 bar,

Tsat = 111.35 C

i.e water boils at 111.35 C when system pressure is 1.5 bar.

Given temperature is below 111.35 C

Therefore, the phase is pure liquid water.

(b) Antoine's equation is given by

log10(Psat[mmHg])=A-B/(T[oC]+C)

At T = 81.3 C

vapor pressure of water Psat = 373.648 mm Hg

Psat = 373.648 mm Hg = 0.498157 bar

By Raoult's Law,

y1P = x1P1sat

x = mole fraction in water, in our case it's pure water, therefore, x = 1

y = mole fraction in the air above

P = system pressure

.: y = 0.498157 / 4 = 0.1245

A B C

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