A catalyst loses its activity due to__________________?

Related Mcqs:

1. 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

2. 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.

3. 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

4. The increase in the rate of reaction with temperature is due to__________________?

   A. Increase in the number of effective collisions
   B. Decrease in activation energy
   C. Increase in the average kinetic energy of the reacting molecules
   D. None of these

5. Overall rate of reaction in a heterogeneous catalytic reaction depends upon the mass and energy transfer from the fluid to solid surface and its rate of reaction is usually ________________ the concentration of catalyst, if it does not entail a chain mechanism?

   A. Proportional to
   B. Independent of
   C. Inversely proportional to
   D. Proportional to the square of

6. The catalytic activity of enzymes is due to their capacity to lower the ______________ energy?

   A. Activation
   B. Potential
   C. Kinetic
   D. None of these

7. Enzymes (a protein) are catalysts found in organisms. Its efficiency of catalysing a reaction is due to its capacity to lower the activation energy of the reaction. The enzyme ptyalin used for food digestion is present in ___________________?

   A. Blood
   B. Saliva
   C. Intestine
   D. Gland

8. If CA is the quantity of reactants initially present, the quantity left after ‘n’ half periods will be equal to__________________?

   A. (CA/2)n
   B. (½)n CA
   C. (CA/2)1/n
   D. (CA)1/2n

9. Catalyst is a substance, which ________________ chemical reaction?

   A. Increases the speed of a
   B. Decreases the speed of a
   C. Can either increase or decrease the speed of a
   D. Alters the value of equilibrium constant in a reversible

10. Bulk diffusion in catalyst pore _______________ with increase in pressure?

    A. Increases
    B. Decreases
    C. Remains unchanged
    D. Increases exponentially