# Separation Processes Questions and Answers – Pervaporation

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This set of Separation Processes Multiple Choice Questions & Answers (MCQs) focuses on “Pervaporation”.

1. Pervaporation method involves
a) Removal of ions
b) Production of potable water
c) Purification of aqueous streams
d) Separation and concentration of liquid mixture.

Explanation: Pervaporation is process of separation and concentration of liquid mixture.

2. When is the pervaporation preferred?
a) When feed solution is dilute in main permeant
b) When feed solution is rich in main permeant
c) When feed solution is dilute in retentate
d) When feed solution is rich in retentate

Explanation: Pervaporation is preferred when the feed solution is dilute in main permeant. If the solution is rich in permeant then more number of membrane stages may be required.

3) Which type of membrane is required for water permeation?
a) Hydrophobic
b) Hydrophilic
c) Semipermeable
d) Permeable

Explanation: When water is to be permeated, hydrophilic membrane is required making the selection of membranes an important factor.

4. What factor is unaccountable in gas permeation?
a) Temperature
b) Polymer
c) Permeant
d) Concentration of permeants

Explanation: The concentration of permeants is not dependent in gas permeation.

5. What are the permeant vales, if permeant flux(N)= 10
For feed side liquid: Y=0.5, x= 0.5
Vapor pressure = 100
Mole fraction of permeant vapor y= 0.25
Total permeant pressure P= 80
a) 2
b) 4
c) 5
d) 7

Explanation: Since Permeance= N/(YxV.P-yP), Permeance= 10/(25-20)=2.

6. What are the permeant vales, if permeant flux(N)= 10
For feed side liquid: Y=0.6, x= 0.5
Vapor pressure = 100
Mole fraction of permeant vapor y= 0.25
Total permeant pressure P= 80
a) 2
b) 4
c) 5
d) 1

Explanation: Since Permeance= N/(YxV.P-yP), Permeance= 10/(30-20)=1.

7. What are the permeant vales, if permeant flux(N)= 10
For feed side liquid: Y=10, x= 0.4
Vapor pressure = 100
Mole fraction of permeant vapor y= 0.5
Total permeant pressure P= 80
a) 20
b) 40
c) 50
d) 0.03

Explanation: Since Permeance= N/(YxV.P-yP), Permeance= 10/(400-40)=0.03.

8. What are the permeant vales, if permeant flux(N)= 10
For feed side liquid: Y=0.5, x= 0.5
Vapor pressure = 100
Mole fraction of permeant vapor y= 0.25
Total permeant pressure P= 60
a) 2
b) 41
c) 1
d) 7

Explanation: Since Permeance= N/(YxV.P-yP), Permeance= 10/(25-15)=1.

9. What are the permeant vales, if permeant flux(N)= 10
For feed side liquid: Y=0.5, x= 0.5
Vapor pressure = 200
Mole fraction of permeant vapor y= 0.25
Total permeant pressure P= 80
a) 1.33
b) 2.55
c) 5.44
d) 7

Explanation: Since Permeance= N/(YxV.P-yP), Permeance= 10/(50-20)=1.33.

10. Incorrect statement about pervaporation is
a) Low cost
b) Independent of vapour/liquid equilibrium
c) Suitable for heat sensible product
d) Require high temperature and high pressure. 