If the pore diffusion controls in a catalytic reaction, the apparent activation energy Ea is equal to___________________?

Related Mcqs:

1. The rate expression for a heterogeneous catalytic reaction is given by, – rA = K.KA PA(1 + KA.PA + KR.PR), where K is surface reaction rate constant and KA and KR are absorption equilibrium constants of A and R respectively. If KR PR >> (1 + KA PA), the apparent activation energy EA is equal to (given E is the activation energy for the reaction and ΔHR and ΔHA are the activation energies of adsorption of R and A) ?

   A. E
   B. E + ΔHA
   C. E + ΔHA – ΔHR)
   D. ΔHA + ΔHR

2. 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

3. 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

4. ‘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.

5. In a reaction, the threshold energy is equal to (where, A = activation energy N = normal energy of reactants) ?

   A. A
   B. N
   C. A + N
   D. A – N

6. When the reaction is dominated by intraparticle diffusion, the apparent order of reaction (nD) as measured is related to the true order (n) as ________________?

   A. nD = (n + 1)/2
   B. nD = n/2
   C. nD = n + 1
   D. None of these

7. A chemical reaction occurs, when the energy of the reacting molecules is ________________ the activation energy of reaction?

   A. Less than
   B. Equal to
   C. More than
   D. Equal to or more than

8. A chemical reaction occurs when the energy of the reacting molecules is __________________ the activation energy of the reaction?

   A. Less than
   B. Equal to
   C. More than
   D. Equal to or more than

9. The minimum energy required to allow a chemical reaction to proceed is termed as the ‘threshold energy ‘. Chemical reactions with low activation energy are ________________?

   A. Always irreversible
   B. Insensitive to temperature changes
   C. Mostly irreversible
   D. Highly temperature sensitive

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