# Mass Transfer Questions and Answers – Fick’s Law-1

This set of Mass Transfer Multiple Choice Questions & Answers (MCQs) focuses on “Fick’s Law-1”.

1. Fick’s law is given by the formula
a) N b = – D b c d C b/d x
b) N b = – 2 D b c d C b/d x
c) N b = – 3 D b c d C b/d x
d) N b = – 4 D b c d C b/d x

Explanation: Experimental evidences shows that molecular diffusion is goverened by the empirical relation suggested by Fick.

2. Figure shows equimolal diffusion between species B and C. Identify the correct molar diffusion rate a) N b = m c/M b
b) N b = m b/M b
c) N c = m b/M b
d) N c = m b/M c

Explanation: Equimolal diffusion between species B and C of a binary gas system implies that each molecule of component B is replaced by each molecule of constituent C.

3. What is the unit of diffusion coefficient?
a) m2
b) s
c) m2 s
d) m2/s

Explanation: D = – N/ (d C/ d x).

4. What is the molecular weight of ammonia?
a) 31
b) 53
c) 29
d) 39

Explanation: Formula of ammonia is NH3.

5. What is the molecular volume of air at normal boiling point?
a) 29.89 cm3/gm mole
b) 39.89 cm3/gm mole
c) 49.89 cm3/gm mole
d) 59.89 cm3/gm mole

Explanation: Air contains some dust particles due to which its molecular volume decreases by a small factor.
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6. What is the value of Schmidt number for hydrogen?
a) 0.23
b) 0.22
c) 0.21
d) 0.21

Explanation: Schmidt number = v/D.

7. Estimate the diffusion coefficient for ammonia in air t 25 degree Celsius temperature and one atmospheric pressure.
For ammonia,
Molecular weight = 17
Molecular volume = 25.81 cm3/gm mole
For air,
Molecular weight = 29
a) 0.4880 cm2/s
b) 0.3880 cm2/s
c) 0.2880 cm2/s
d) 0.1880 cm2/s

Explanation: D = 0.0043 T 3/2/p t (V b1/3 + V c1/3) 2 [1/M b + M c] ½.

8. Estimate the diffusion coefficient of carbon monoxide through air in which the mole fractions of each constituents are
O 2 = 0.18
N 2 = 0.72
CO = 0.10
The gas mixture is at 300 K and 2 atmosphere total pressure. The diffusivity values are
D CO = 18.5 * 10 -6 m2/s at 273 K, 1 atm
D CN = 19.2 * 10 -6 m2/s at 288 K, 1 atm
The subscripts C is carbon monoxide, O is oxygen and N is nitrogen
a) 10.29 * 10 -6 m2/s
b) 18.5 * 10 -6 m2/s
c) 17.5 * 10 -6 m2/s
d) 13.5 * 10 -6 m2/s

Explanation: (T 1/T 2) 3/2 (p 2/p 1) = D 1/D 2.

9. What is the molecular weight of Sulphur-dioxide?
a) 84
b) 74
c) 64
d) 54

Explanation: Formula of Sulphur-dioxide is SO 2.

10. The dimension of diffusion coefficient is given by
a) M L T -2
b) L 2 T -1
c) L T -1
d) M L -2 T

Explanation: Unit is m2/s.

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. 