# Separation Processes Questions and Answers – Binary Vapor-Liquid System

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This set of Separation Processes Multiple Choice Questions & Answers (MCQs) focuses on “Binary Vapor-Liquid System”.

1. Which of the following is the correct formula for gibb’s phase rule?
a) F=c+p
b) F=c+p-2
c) F=c-p-2
d) F=c*p -2

Explanation: The correct formula for gibb’s phase rule is F=c+p-2.

2. What are the degrees of freedom if there are two components in two phases?
a) 0
b) 2
c) 4
d) 6

Explanation: Since F=c+p-2, when c=2 and p=2, F= 2+2-2=2.

3. Which of the following is not true?
a) yB= 1- yA
b) xB = 1-xA
c) yA= 1- yB
d) xB= 1- yB

Explanation: xB= 1- yB is incorrect since xb+yb is not equal to 1.

4. Which of the following techniques is not used when the boiling point difference is too small?
a) Crystallization
c) Distillation
d) Zone melting

Explanation: Distillation is impractical when the boiling point difference is too small since large amount of trays are required for obtaining pure products.

5. Which of the following is correct definition of bubble point?
a) Boiling point
b) Temperature at which bubbles start
c) Temperature at which pressure of bubbles is highest
d) Temperature at which first bubble comes

Explanation: The temperature at which the first bubble is seen is called the bubble point.

6. What is the definition of critical point?
a) The temperature or pressure beyond which the liquid-vapor cannot co-exist
b) The temperature or pressure beyond which the liquid-liquid mixture cannot co-exist
c) The temperature or pressure beyond which the vapor vanishes
d) The temperature or pressure beyond which the bubbles start coming

Explanation: The temperature or pressure beyond which the liquid-vapor cannot co-exist and yA=xA.

7. What is the correct definition of dew point?
a) The point at which first drop of gas boils
b) The point at which the first drop of liquid boils
c) The point at which the first drop of gas condenses
d) The point at which the bubble comes

Explanation: Dew point is the point at which the first drop of gas condenses.

8. When does the relative volatility vary little with pressure?
a) For broad boiling point mixture showing non-ideal behavior
b) For narrow boiling point mixtures showing non-ideal behavior
c) For narrow boiling point mixtures showing ideal behavior
d) For broad boiling point mixtures showing idal behavior

Explanation: The relative volatility varies little with pressure for narrow boiling point mixtures showing ideal behavior.

9. From the knowledge of vapor pressures of components, a y=x equilibrium can be approximated using how many values of αA,B?
a) Zero
b) One
c) Two
d) Three

Explanation: From the knowledge of vapor pressures of components, a y=x equilibrium can be approximated using only one value of αA,B.

10. Which of the following is untrue about Roult’s law?
a) P=PAsxA + PBsxB
b) P=PAsxA + PBs(1-xA)
c) P= PAsxA + PAs(1-xA)
d) P=PsB + xA(PsA-PsB)

Explanation: All other forms are correct except P= PAsxA + PAs(1-xA).

Sanfoundry Global Education & Learning Series – Separation Processes.

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