Please show all work. Just checking mine with yours, I am getting a different an

Question

Please show all work. Just checking mine with yours, I am getting a different answer from my instructor so I need to see what i am doing wrong

[Raoult’s law + Condensable vapor + uncondensablegas mixture] A mixture of condensable species A & B is in equilibrium with an uncondensable insoluble gas C (pC=7mmHg). At T=25°C, it is found that pA*=10 mmHg and pB*=20 mmHg. If xA=0.3

a) Calculate the partial pressures, pA and pB

ans: pA=3mmHg, pB=14mmHg

b) Total pressure P=?

ans: P=24mmHg

c) Calculate the vapor fractions

ans: yA=0.125 yB=0.583 yC=0.292

Explanation / Answer

Part a

From the Raoult’s law

Partial pressure of A = vapor pressure of A × mol fraction of A

pA = pA* × xA

= 10 mmHg × 0.3 = 3 mmHg

Partial pressure of B = vapor pressure of B × mol fraction of B

pB = pB* × xB

= 20 mmHg × (1-0.3)

= 14 mmHg

Part b

Total pressure = pA + pB + pC

= 3 + 14 + 7

= 24 mmHg

Part c

yA × P = pA

yA = 3/24 = 0.125

yB = pB/P

= 14/24 = 0.583

yC = 1 - 0.125 - 0.583

= 0.292

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