Mass Transfer Questions and Answers – Molecular Diffusion in Solids

This set of Mass Transfer Multiple Choice Questions & Answers (MCQs) focuses on “Molecular Diffusion in Solids “.

1. Find the operation where diffusion of solids not occurs
a) Adsorption
b) Leaching
c) Drying
d) Distillation
View Answer

Answer: d
Explanation: Distillation is the liquid-liquid operation where no diffusion on solid is possible.

2. Find the diffusivity through slab if N flux of A 4 mol/sq.m sec, concentration difference is 2mol/cu.m and distance is 3 m.
a) 2 sq.m/s
b) 4 sq.m/s
c) 6 sq.m/s
d) 8 sq.m/s
View Answer

Answer: c
Explanation: N flux of A= D(AB)/z * concentration difference
D(AB) = 6 sq.m/sec.

3. Find the activated diffusivity of carbon if energy of activation is 6 kJ; the value of constant diffusivity is 2.5 sq.m/sec. (Hint: the value of exponential of (-6/RT) is 2.55)
a) 6.375 sq.m/s
b) 1.02 sq.m/s
c) 15.3 sq.m/s
d) 16.25 sq.m/s
View Answer

Answer: a
Explanation: Activated diffusivity= constant diffusivity * exponential value
= 2.5 * 2.55
= 6.375.
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4. The term activated means _____________
a) Pressure dependency
b) Temperature dependency
c) Volume dependency
d) None of the mentioned
View Answer

Answer: b
Explanation: Activated represents the activation energy which depends on temperature.

5. If the two gases are separated by a polymer membrane, the extent of diffusion depends on _______ law.
a) Hendy
b) Raoult
c) Newton
d) None of the mentioned
View Answer

Answer: a
Explanation: Concentration is directly proportional to pressure so Hendry law is applicable.

6.For permanent gases diffusivity the order is _________ sq.m/s
a) 10-7
b) 10-8
c) 10-9
d) 10-10
View Answer

Answer: d
Explanation: The gas can become permeable to certain substance if it is in an order of 10-10.

7. The solute movement of fluid on solids are __________
a) Hygrodynamic
b) Hydrodynamic
c) Fluid dynamic
d) None of the mentioned
View Answer

Answer: b
Explanation: Solute movement is due to pressure difference which is hydrodynamic.
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8. If the pore of the solid is inaccessible to external fluids then it is known as dead end.
a) True
b) False
View Answer

Answer: b
Explanation: If the pore of the solid is inaccessible to external fluids then it is known as isolate.

9. Macroporic surrounding of microscopic pellets powders of different magnitude in size is _______
a) Disperse
b) Bi-disperse
c) Tri-disperse
d) None of the mentioned
View Answer

Answer: b
Explanation: The double surrounding of these pellets is known as bi-disperse.
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10. Find the permeability if diffusivity is 2 units and solubility coefficient is 5 units assume all are in SI units.
a) 10 units
b) 2.5 units
c) 0.4 units
d) None of the mentioned
View Answer

Answer: a
Explanation: Permeability = solubility co-efficient * diffusivity
= 2 * 5 =10 units.

Sanfoundry Global Education & Learning Series – Mass Transfer.

To practice all areas of Mass Transfer, here is complete set of 1000+ Multiple Choice Questions and Answers

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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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