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

Related Mcqs:

1. ‘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.

2. A first order reaction A → B occurs in an isothermal porous catalyst pellet of spherical shape. If the concentration of A at the centre of the pellet is much less than at the external surface, the process is limited by__________________?

   A. Diffusion within the pellet
   B. Reaction
   C. External mass transfer
   D. None of the above

3. Effectiveness factor E. of a catalyst pellet is defined as, E = (actual rate within pore of the catalyst)/(rate if not snowed by pore diffusion), Effectiveness factor for a first order reaction is given by (where, T = Thiele modulus) ___________________?

   A. tan hT/T
   B. tan T/T
   C. tan hT/tan T
   D. None of these

4. Effectiveness factor of a catalyst pellet is a measure of the _________________ resistance?

   A. Pore diffusion
   B. Gas film
   C. Chemical reaction
   D. None of these

5. Which of the following factors control the deactivation of a porous catalyst pellet?

   A. Decay reactions
   B. Pore diffusion
   C. Form of surface attack by poison
   D. All A., B. and C.

6. Knudsen diffusion is directly proportional to _____________________?

   A. T
   B. √T
   C. 1/√T
   D. T2

7. A catalyst is said to be a negative catalyst, if it ___________________?

   A. Retards the rate of reaction
   B. Reduces the value of equilibrium constant
   C. Does not initiate the reaction
   D. All A., B. and C.

8. 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

9. The eddy diffusivity for a liquid in plug flow must be_________________?

   A. 1
   B. 0
   C. ∞
   D. Between 0 and 1

10. Catalytic action in a catalytic chemical reaction follows from the ability of catalyst to change the ___________________?

    A. Activation energy
    B. Equilibrium constant
    C. Heat of reaction
    D. None of these