250+ TOP MCQs on Non Ideal Flow Basics – RTD for Combination of Reactors and Answers

1. State true or false.
A corner peak in the E(t) indicates bypassing of reactants.
A. True
B. False
View Answer

Answer: A
Explanation: Corner peak is an identification of reactor bypassing. It is because the reactants bypassed appear on the reactor outlet as soon as they are fed in.

3. If the residence time obtained for a reactor by the RTD experiments is less than that expected, it indicates the presence of ____
A. CSTR
B. PFR
C. Bubbling bed reactor
D. Dead volume
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Answer: D
Explanation: The dead volume of a reactor does not contribute to the reactor function. The entire volume of a reactor is the sum of the active volume and dead volume.

4. If the entire volume of a PFR is 10 m³ and dead volume is 2 m³, then the active volume of the reactor is ____
A. 20
B. 5
C. 8
D. 12
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Answer: C
Explanation: Volume of PFR, V = Vp + Vd
Vp is the active volume of PFR and Vd is the dead volume.
10 = Vp + 2
Vp = 2.

6. State true or false.
The exit age distribution for the series combination of a PFR followed by a CSTR is same as that for CSTR followed by a PFR.
A. True
B. False
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Answer: A
Explanation: There is no axial mixing in a PFR. The output of the PFR is delayed no matter it is arranged in front of CSTR or following CSTR.

7. For two PFRs P₁ and P₂ in parallel, the exit age distribution gives ____
A. A single peak at t = t_p1
B. A single peak at t = t_p2
C. Two peaks, one at t = t_p1 and the other at t = t_p2
D. A corner peak
View Answer

Answer: C
Explanation: Two peaks are obtained. One is at t_p1 = (frac{V_{p1}}{v_1}) another is at t_p2 = (frac{V_{p2}}{v_2}. )
v₁ and v₂ are the volumetric flowrates in P₁ and P₂, respectively.

8. The variance of a PFR is ____
A. 1
B. 0
C. ∞
D. -1
View Answer

Answer: B
Explanation: There is no mixing inside a PFR. There is no variation in the concentration in the PFR.

9. The variance of a CSTR is ____
A. 1
B. 0
C. ∞
D. -1
View Answer

Answer: C
Explanation: There is complete mixing inside a CSTR. The reactants are uniformly mixed. Hence, there is a variation in CSTR.