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

1. Before collision, the distance between the two particles is mean free path.

a) True

b) False

View Answer

Explanation: The mean free path can be found after collision.

2. Diffusion co-efficient in molecular diffusion is estimated by _________

a) Daltons law

b) Diffusion law

c) Ficks law

d) None of the mentioned

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Explanation: Fick’s law is the ratio of J-flux to the concentration gradient.

3. Find the total flux for a particle A and B in a steady state if flux of A and B is 2.44 and 4.44 mol/sq.m sec.

a) 2

b) 4.88

c) 6.88

d) 8

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Explanation: Total flux= flux A+ flux B= 6.88.

4. Find the flux of A ( xA= 0.2) if Total flux is 5 mol/sq.m sec and J flux of A is 2 mol/sq.m sec.

a) 2

b) 2.5

c) 3

d) 3.5

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Explanation: N flux of A = J flux of A + Total flux N * xA

= 2+ 0.5*2 = 3.

5. Find J flux of A ( xA = 0.5) if the total N flux is 6 mol/sq.m sec and N flux of A is 3 mol/sq.m sec.

a) 0

b) 1

c) 2

d) 3

View Answer

Explanation: N flux of A = J flux of A + Total flux N * xA

3= J flux of A + 6 * 0.5

J flux = 0.

6. Diffusivity of the liquids can be determined by

a) Wilke- lee equation

b) Wilke- chan equation

c) Lee and chan equation

d) None of the mentioned

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Explanation: Wilke- Chan derived an equation for diffusivity of liquids.

7. For the molecular diffusion of liquids, if the diffusing molecules having criteria of steady state diffusion of B over non diffusing A then the N flux of A is

a) 1

b) 0

c) Negative

d) Infinity

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Explanation: For non-diffusing A then N flux of B is zero.

8. For liquid molecular diffusion of A and B, steady state equimolar counter diffusion the N flux of A is negative of N flux of B.

a) True

b) False

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Explanation: For equimolar counter diffusion, the one component flux is negative of other.

9. Find the change in concentration for a steady state equimolar counter diffusion if D(AB)= 6 sq.m/sec, the change in distance is 2 m and the N flux of A is 5 mol/sq.m sec.

a) 0.67

b) 1.67

c) 2.67

d) None of the mentioned

View Answer

Explanation: N flux of A = D(AB)/z * (Concentration difference)

Concentration difference = 5/3 =1.67.

10. Find the diffusivity of AB in sq.m/sec if N flux of A 5 mol/sq.m sec, concentration difference is 2mol/cu.m and distance is 3 m.

a) 2.5

b) 5.5

c) 7.5

d) 10.5

View Answer

Explanation: N flux of A= D(AB)/z * concentration difference

D(AB) = 7.5 sq.m/sec.

**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__