250+ TOP MCQs on Bypass and Purge and Answers

Basic Chemical Engineering Multiple Choice Questions & Answers (MCQs) on “Bypass and Purge”.

1. A bypass stream does not go through which of the following?
a) Mixer
b) Process
c) Separator
d) None of the mentioned
Answer: b
Clarification: A bypass stream directly goes from divider to separator skipping the process.

2. Which of the following does the purge stream comes from?
a) Feed stream
b) Product stream
c) Recycle stream
d) None of the mentioned
Answer: c
Clarification: Purge stream is the removal of unwanted material from the recycle stream.

3. Which of the following composition can be controlled by a bypass stream?
a) Exit stream
b) Feed
c) Process
d) None of the mentioned
Answer: a
Clarification: Bypass stream can be used to control the composition of a final stream.

4. Which of the following composition is controlled by purge stream?
a) Feed
b) Product stream
c) Recycle stream
d) None of the mentioned
Answer: c
Clarification: Composition of recycle stream can be controlled by purge stream.

5. Which of the following is decreased by the bypass stream?
a) Feed
b) Product
c) Feed & Product
d) None of the mentioned
Answer: a
Clarification: Bypass stream decreases the feed and increases the product.

Answer question 6 – 10 for the following diagram.

6. What is the value of P?
a) 5 mole/hr
b) 10 mole/hr
c) 15 mole/hr
d) 20 mole/hr
Answer: c
Clarification: Overall CH₄ balance: 0.6*20 = 0.8*P, => P = 15 mole/hr.

7. What is the value of W?
a) 5 mole/hr
b) 10 mole/hr
c) 20 mole/hr
d) 25 mole/hr
Answer: a
Clarification: Overall C₂H₆ balance: 0.4*20 = 0.2*15 + 1*W, => W = 5 mole/hr.

8. What is the value of G?
a) 12.5 mole/hr
b) 25 mole/hr
c) 37.5 mole/hr
d) 50 mole/hr
Answer: a
Clarification: Material balance: G = 5 + H, CH₄ balance: G(0.6) = H, solving both equations G = 12.5 mole/hr.

9. What is the value of H?
a) 5 mole/hr
b) 7.5 mole/hr
c) 10 mole/hr
d) 12.5 mole/hr
Answer: b
Clarification: H = 0.6G = 7.5 mole/hr.

10. What is the value of B?
a) 7.5 mole/hr
b) 15 mole/hr
c) 20 mole/hr
d) 22.5 mole/hr
Answer: a
Clarification: B = F – G = 20 – 12.5 = 7.5 mole/hr.

Answer question 11 – 15 for the following diagram. The reaction is N2 + 3H2 -> 2NH3, overall conversion of N2 is 80%.

11. What is the value of W?
a) 2.5 mole
b) 5 mole
c) 9.5 mole
d) 20 mole
Answer: a
Clarification: 0.2*10 = 0.8*1*W, => W = 2.5 mole.

12. What is the value of P?
a) 2.5 mole
b) 5 mole
c) 7.5 mole
d) 10 mole
Answer: c
Clarification: F = W + P, => 10 = 2.5 + P, => P = 7.5 mole.

13. What is the fraction of N2 in purge stream?
a) 0.04
b) 0.05
c) 0.16
d) 0.4
Answer: b
Clarification: N₂ balance: 10*0.2 – 10*0.2*0.8 = 7.5*x, => x = 0.05.

14. How many moles of H₂ are recycled?
a) 1.5
b) 2.2
c) 2.8
d) 3.9
Answer: d
Clarification: Moles of H₂ in G stream = 10*0.8 – 3*10*0.2*0.8 = 3.2 = moles of H₂ in H stream. Moles of H₂ in P stream = 0.95*7.5 = 7.125, => moles of H₂ in R stream = 7.125 – 3.2 = 3.925.

15. What is the value of R?
a) 1.4
b) 2.8
c) 4.2
d) 6.8
Answer: c
Clarification: Recycled moles of H₂ = 3.925, recycled moles of N₂ = (10*0.2 – 10*0.2*0.8) – 0.05 = 0.35, => R = 3.925 + 0.35 = 4.275.