Separation Processes Questions and Answers – Two Film Theory and Overall Mass transfer Coefficients

This set of Separation Processes Interview Questions and Answers for Experienced people focuses on “Two Film Theory and Overall Mass transfer Coefficients”.

1. What results due to addition of surfactants?
a) Ease of diffusion
b) Interfacial mass transfer resistance
c) Ease of mass transfer
d) A cloud over the liquid interface
View Answer

Answer: b
Explanation: The surfactants which reduce the surface tension results in Interfacial mass transfer resistance.

2. Which of the following is true about rate of mass transfer in gas?
a) NA = kp(pab-pai)
b) NA = kp(cab-cai)
c) NA = kc(pab-pai)
d) NA = kc(cab-cai)
View Answer

Answer: a
Explanation: For diffusion in gas, partial pressure of the gas is considered.

3. Which of the following is true about rate of mass transfer in liquid?
a) NA = kp(pab-pai)
b) NA = kp(cab-cai)
c) NA = kc(pab-pai)
d) NA = kc(cab-cai)
View Answer

Answer: d
Explanation: For mass transfer in liquid, molar concentration is considered.
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4. Which of the following is the incorrect form of Henry’s law?
a) pA=HAxA
b) pA = cA/HA
c) Xa=HAxA
d) YA = HAxA
View Answer

Answer: c
Explanation: All are the correct forms of henry’s law except Xa=HAxA.

5. Which of the following is true about overall mass transfer coefficient KL?
a) KL =HA/kp +1/kc
b) 1/KL = HA/kp +1/kc
c) KL =1/HA kp +1/kc
d) 1/KL = HA/kp +kc
View Answer

Answer: b
Explanation: Using henry’s law and slope point form in the graph we get 1/KL = HA/kp +1/kc.
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6. What is the correct expression for overall mass transfer coesfficient based on mole fraction driving forces?
a) 1/Kx = 1/KAky + 1/kx
b) Kx = 1/KAky + 1/kx
c) 1/Kx = KA/ky + 1/kx
d) 1/Kx = 1/KAkx + 1/ky
View Answer

Answer: a
Explanation: 1/Kx = 1/KAky + 1/kx is the correct representation of overall mass transfer coefficient.

7. What will be the overall mass transfer coefficient when the resistance by gas phase is negligible?
a) 1/Kx = 1/KAky + 1/kx
b) Kx = 1/KAky + 1/kx
c) 1/Kx = KA/ky + 1/kx
d) 1/Kx = 1/KAkx + 1/ky
View Answer

Answer: b
Explanation: When the resistance by gas is negligible 1/KAky>>1/kx.
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8. What are the correct SI units for kx, ky?
a) kmol/s-m
b) kmol/s-m2
c) mol/s-m2
d) kmol/s
View Answer

Answer: b
Explanation: The SI units for kx and ky is kmol/s-m2.

9. Which of the following is true for mass transfer across liquid-liquid interface?
a) 1/Kx(2) = 1/KAkx(1) + 1/ky(2)
b) 1/Kx(2) = 1/KAky(2) + 1/kx(2)
c) 1/Kx(2) = 1/KAkx(1) + 1/kx(2)
d) 1/Kx(2) = 1/ky(1) + 1/kx(2)
View Answer

Answer: c
Explanation: For mass transfer across liquid-liquid interface 1/Kx(2) = 1/KAkx(1) + 1/kx(2) holds true.
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10. What is the SI unit of kp?
a) kmol/s-m2-pa
b) kmol/s-m-kpa
c) kmol/m2-kpa
d) kmol/s-m2-kpa
View Answer

Answer: d
Explanation: The value of kp involes partial pressure and its SI unit is kmol/s-m2-kpa.

Sanfoundry Global Education & Learning Series – Separation Processes.

To practice all areas of Separation Processes for Interviews, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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