★Specialized Examination for Chemical Engineering ★ — One question per day (2016-1-22) — Points are awarded for participation
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Points system for the daily question: Participation – 1~3 points; Correct answer – 5 points; In-depth analysis – 5~10 points. The answer is provided the next day. Due to limited capabilities, I am unable to provide more in-depth explanations for each question; therefore, on the second day, in addition to offering reference options, I will also remove the restriction on reading replies. I hope that all candidates can learn from one another and improve together! Daily Question (2016-1-22): 1. Components A and B form an ideal gas-liquid equilibrium system. The mole fraction of A in the liquid phase is XA = 0.9, and the relative volatility is 3. Then the mole fraction of the component with the lower boiling point in the gas phase is: A. 0.95 B. 0.53 C. 0.45 D. 0.25 Answer: A
The correct answer to this question should be A. Low boiling point refers to components that are volatile; the relative volatility of A is 3, so A is the volatile component. Therefore, (ya/xa)/(yb/xb) = 3. With xa = 0.9 and xb = 1 – 0.9 = 0.1, we get ya/yb = 3 × 0.9 = 27. Hence, ya = 27 / (27 + 1) = 0.96.
The answer can be calculated using the gas-liquid phase equilibrium equation; choose A
This post was last edited by f9kx on 2016-1-22 09:47. D．0.25 y*0.9/(0.1*(1-y))=3. Hah… It should be: y*0.1/(0.9*(1-y))=3, or the gas-liquid equilibrium equation can be used directly; the answer is 0.96
1. The system consisting of components A and B is in an ideal gas-liquid equilibrium state. The molar fraction of A in the liquid phase is XA = 0.9, and the relative volatility is 3. Then the molar fraction of the component with the lower boiling point in the gas phase is: (A) A. 0.95 B. 0.53 C. 0.45 D. 0.25