# Separation Processes Questions and Answers – Rate Based Method for Packed Columns

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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

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 /NT
d) HETP = lT+NT

Explanation: The formula for HETP is HETP = lT/NT where lT 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

Explanation: At the interface of liquid and vapor, a physical equilibrium exists.
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4. Which of the following is the correct illustration of rate of mass transfer?
a) r= ky a(y-y 1 ) =kx a(x-x 1 )
b) r= ky a(y 1 -y) =kx a(x 1 -x)
c) r= ky a(y-y 1 ) =kx a(x 1 -x)
d) r= a(y-y 1 ) =a(x 1 -x)

Explanation: r= k y a(y-y 1 ) =k xa(x 1 -x) is the correct illustration for rate of adsorption where kya 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/Ky a = 1/ky a +K/Kx a
b) 1/Ky a = 1/ky a +K/Ky a
c) 1/Ky a = 1/ky a +1/KKx a
d) Ky a = 1/ky a +K/Kx a

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

Explanation: HOG = V/ky 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

Explanation: HOG = V/ky 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

Explanation: HOG = V/ky 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

Explanation: HETP =lT /NT , hence lT =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

Explanation: HETP =lT /NT , hence lT =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

Explanation: HETP =lT /NT , hence lT =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

Explanation: HETP =lT /NT , hence lT =4.2*2=8.4.

Sanfoundry Global Education & Learning Series – Separation Processes.

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