# Mass Transfer MCQ’s – Fick’s Law-1

1 - Question

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 - Question

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 - Question

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 - Question

What is the molecular weight of ammonia?
a) 31
b) 53
c) 29
d) 39
Explanation: Formula of ammonia is NH3.

5 - Question

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.

6 - Question

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 - Question

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 - Question

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 - Question

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 - Question

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