This set of Separation Processes Multiple Choice Questions & Answers (MCQs) focuses on “Rate Based Method for Packed Columns”.

1. Packed columns are better analyzed by:

a) Mass transfer coefficients

b) Equilibrium stage methods

c) Graphical methods

d) Algebraical methods

View Answer

Explanation: Packed columns are better analyzed by mass transfer coefficients.

2. What is the formula for HETP or HETS?

a) HETP = l_{ T} *N _{T}

b) HETP = l _{T}-N _{T}

c) HETP = l _{T} /N_{T}

d) HETP = l_{T}+N_{T}

View Answer

Explanation: The formula for HETP is HETP = l

_{T}/N

_{T}where l

_{T}is the packed height length and the N T is the number of equilibrium stages.

3. At the interface of liquid and vapor, which interface exists?

a) Chemical

b) Physical

c) Thermal

d) No equilibrium exists

View Answer

Explanation: At the interface of liquid and vapor, a physical equilibrium exists.

4. Which of the following is the correct illustration of rate of mass transfer?

a) r= k_{y} a(y-y 1 ) =k_{x} a(x-x 1 )

b) r= k_{y} a(y 1 -y) =k_{x} a(x 1 -x)

c) r= k_{y} a(y-y 1 ) =k_{x} a(x 1 -x)

d) r= a(y-y 1 ) =a(x 1 -x)

View Answer

Explanation: r= k

_{y}a(y-y 1 ) =k

_{x}a(x 1 -x) is the correct illustration for rate of adsorption where k

_{y}a and k

_{x}a are volumetric mass transfer coefficients.

5. Which of the following is the correct representation of overall mass transfer coefficient?

a) 1/K_{y} a = 1/k_{y} a +K/K_{x} a

b) 1/K_{y} a = 1/k_{y} a +K/K_{y} a

c) 1/K_{y} a = 1/k_{y} a +1/KK_{x} a

d) K_{y} a = 1/k_{y} a +K/K_{x} a

View Answer

Explanation: The correct representation of overall mass transfer coefficient is 1/K y a = 1/k y a +K/K x a, where K y is the overall mass transfer coefficient obtained from slope=point form.

6. What is the overall height of gas transfer unit if the volume is 1000m 3 and the overall gas phase coefficient is 2.6 and the inside cross sectional area is 20m 2 .

a) 12m

b) 13.6m

c) 18.9m

d) 19.2m

View Answer

Explanation: HOG = V/k

_{y}aS, hence HOG= 1000/2.6*20=19.2.

7. What is the overall height of gas transfer unit if the volume is 780m 3 and the overall gas phase coefficient is 4.2 and the inside cross sectional area is 45m 2 .

a) 4.1m

b) 7.2m

c) 10.4m

d) 19.2m

View Answer

Explanation: HOG = V/k

_{y}aS, hence HOG= 780/4.2*45=4.1.

8. What is the overall height of gas transfer unit if the volume is 489m 3 and the overall gas phase coefficient is 1.2 and the inside cross sectional area is 22m 2 .

a) 12m

b) 13.6m

c) 18.5m

d) 19.2m

View Answer

Explanation: HOG = V/k

_{y}aS, hence HOG= 489/1.2*22=18.5.

9. What is the packed height length is HETP is 3ft and the number of equilibrium stages is

a) 0.75

b) 1.33

c) 12

d) 16

View Answer

Explanation: HETP =l

_{T}/N

_{T}, hence l

_{T}=4*3=12.

10. What is the packed height length is HETP is 3.8ft and the number of equilibrium stages is

a) 0.76

b) 1.3157

c) 12

d) 19

View Answer

Explanation: HETP =l

_{T}/N

_{T}, hence l

_{T}=3.8*5=19.

11. What is the packed height length is HETP is 6ft and the number of equilibrium stages is

a) 0.76

b) 1.3157

c) 30

d) 19

View Answer

Explanation: HETP =l

_{T}/N

_{T}, hence l

_{T}=6*5=30.

12. What is the packed height length is HETP is 4.2ft and the number of equilibrium stages is

a) 0.76

b) 8.4

c) 12

d) 19

View Answer

Explanation: HETP =l

_{T}/N

_{T}, hence l

_{T}=4.2*2=8.4.

**Sanfoundry Global Education & Learning Series – Separation Processes.**

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