# Distillation Design Questions and Answers – Constant Reflux Ratio

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This set of Distillation Design Multiple Choice Questions & Answers (MCQs) focuses on “Constant Reflux Ratio”.

1. Which one of the following is a constant reflux process?
a) Flash distillation
b) Simple distillation
c) Multicomponent distillation
d) Final distillation

Explanation: Simple or batch distillation is working on the constant reflux in such a distillation compositions continuously vary with time.

2. Batch distillation under constant reflux can be analyzed?
a) –dw=dD
b) dv=-dx
c) – dy=dZ
d) dX=dy

Explanation: –dw = dD where,W= Still moles and D= moles of distillate.

3. The initial mole Yint fraction of gas, can be obtained by
a) Xd/R+1
b) –dw=dD
c) – dy=dZ
d) R+1

Explanation: Yint fraction of gas can be obtained by Xd/R+1, Where Yint=value of y at x =0.
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4. As the distillation proceeds, the L/V ratio
a) Constant
b) Decreases
c) Increases
d) Vanishes

Explanation: The distillation and the L/V ratio are directly proportional and thus as distillation proceeds L/V Increases.

5. Calculate V? If D = 52.2 moles and R is 1.64
a) 138 moles
b) 35 moles
c) 450 moles
d) 46 moles

Explanation: As the V = D(R+1) = 52.2 (1.64+1) = 138 moles.

6. If the area of the column is 3.61 m2 and the initial and final distilled moles are 0.95 and 0.50 with Withdrawal of 100 moles, then V is?
a) 162
b) 456
c) 78
d) 45

Explanation: As V= W0 (Xd – X0) (Area) = 100 (0.95-0.50)3.61 = 162 moles.

7. The Antoine equation is given as
a) ln VP = B –A/CT
b) ln VP =A – B/T
c) ln VP = B – A/T
d) ln VP = B -CA

Explanation: The Antoine equation is ln VP =A – B/T where A, B and C are constants and VP is the vapor pressure.

8. Find R? If Xd = 0.98 and Yi =0.647
a) 0.633
b) 0.589
c) 0.515
d) 0.25

Explanation: As R = Xd/ Yi – 1 = 0.98/0.647 – 1 = 0.515.

9. The Ract can be taken, as
a) 1.3Rmin
b) 1.6 Rmin
c) 2.0 Rmin
d) 3.0 Rmin

Explanation: For a particulate separation the actual reflux ratio is taken as to be twice the actual reflux ratio i.e. Rmin.

10. Calculate feed line q? If HV=31,067, HF=34,601 and Hl= 0
a) -0.114
b) -0.36
c) -0.556
d) 0.885

Explanation: As q = ( HV- HF)/( HV- Hl) = (34,067-34,601)/(34,067-0) = -0.114.

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