Knudsen diffusion is directly proportional to _____________________?

Related Mcqs:

1. Effective diffusivity (DE) in a catalyst pellet is related to molecular diffusivity (DN) and Knudsen diffusivity (DK) as_________________?

   A. DE = DM + DK
   B. 1/DE = 1/DN + DK
   C. DE = DM . DE
   D. DE = DN/DE

2. ‘If the catalyst pore size is small in comparison with the mean free path, collisions with the pore wall controls the process’. The diffusivity under this condition is called ‘Knudsen diffusivity’, which is affected by the_____________________?

   A. Pressure
   B. Temperature
   C. Both A. & B.
   D. Neither A. nor B.

3. According to the ‘law of mass action’, the rate of reaction is directly proportional to the__________________?

   A. Equilibrium constant
   B. Volume of the reaction vessel
   C. Nature of the reactants
   D. Molar concentration of the reactants

4. In a chemical reaction, represented by as shown in the bellow figure, it is observed that the (i) Rate of reaction increases by a factor of 4 on doubling the concentration of the reactant. (ii) Rate of reaction increases by a factor of 9 on trebling the concentration of the reactant. Then the rate of the reaction is proportional to(where, CA = concentration of the reactant)_____________________?

   A. CA
   B. CA2
   C. CA3
   D. CA4

5. The rate at which a chemical substance reacts is proportional to its _____________________?

   A. Active mass
   B. Molecular weight
   C. Equivalent weight
   D. Atomic weight

6. If pore diffusion is the controlling step in a solid catalysed reaction, the catalyst___________________?

   A. Porosity is very important
   B. Porosity is of less importance
   C. Internal surface area is utilised efficiently
   D. None of these

7. Which of the following is not a dimension-less group used in catalysis? (Where, D = dispersion co-efficient, cm2/sec.D1 = diffusion co-efficient; cm2/sec L = length of the reactor, cm t = time, sec, v = volumetric flow rate, cm3/sec. V = volume, cm3.) ?

   A. Reactor dispersion number (D/vL)
   B. Reduced time (vt/V)
   C. Thiele modulus L √(k/D1)
   D. None of these

8. If Thiele modulus is ________________, then the pore diffusion resistance in a catalyst may be considered as negligible?

   A. 0
   B. ∞
   C. < 0.5
   D. > 0.5

9. When the reaction occurs in the diffusion controlled region, the apparent activation energy as measured is only _______________ the true value?

   A. Twice
   B. Half
   C. Equal
   D. None of these

10. A spherical porous catalyst particle of radius R is subjected to reactant A which reacts to form B by a zero order surface reaction A → B. Film mass transfer resistance is negligible and pore diffusion of A is rate controlling. The effectiveness factor of the catalyst is reported as 7/8. Which of the following statement is true?

    A. Inner catalyst core of radius R/8 does not participate in reaction
    B. Inner catalyst core of radius R/2 does not participate in reaction
    C. Inner catalyst core of radius 7R/8 does not participate in reaction
    D. Effectiveness factor for a zero order reaction cannot be 7/8 as it must always be 1