Mass Transfer Practice Test 10

1. 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.

2.5

10.5

7.5

5.5

2. 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)

15.3 sq.m/s

6.375 sq.m/s

1.02 sq.m/s

16.25 sq.m/s

3. The value of N flux of A under steady state non-diffusing B with diffusing A is _________

None of the mentioned

Infinity

Constant

4. If all the components except 1 of the multicomponent diffusing mixture are inert, then what will be the expression for Diffusivity of component 1 in the mixture?

D_1m=(1-Y₁)/(∑[Y_j/D_ij])

D_1m=(Y₁∑N_j)/(∑(Y_jN₁-Y₁N_j)/D_ij)

D_1m=(N₁-Y₁∑N_j)/(∑(Y_jN₁-Y₁N_j)/D_ij)

D_1m=N₁/(∑[(Y_jN₁-Y₁N_j)/D_ij])

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.

6. Sublimation of a long cylinder made of napthelene occurs in a large volume of stagnant air. The time required for its complete sublimation is

half the time of sublimation of a sphere of the same mass

infinite

twice the time of sublimation of a cylinder of the same mass and lengthy/diameter=1

half the time of sublimation of a cylinder of the same mass and lengthy/diameter=1

7. If the value of N flux of A to the total N flux is 1 then it is a steady state diffusion of non-diffusing B.

True

False

8. If the two gases are separated by a polymer membrane, the extent of diffusion depends on _______ law.

Raoult

None of the mentioned

Hendy

Newton

9. For a Steady state diffusion of A through Non- diffusing B. N flux of B= ______

Infinity

10. 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.

False

True