Chemical Reaction Engineering – Multiple Choice Questions (MCQs)

1. 37. What does a large Thiele modulus indicate?

   • A. Reaction rate is limited by diffusion
   • B. Reaction rate is not limited by diffusion
   • C. High effectiveness factor
   • D. Low effectiveness factor

2. 38. What is 'external diffusion resistance'?

   • A. Resistance to mass transfer from the bulk fluid to the external surface of the catalyst pellet
   • B. Resistance within the catalyst pellet
   • C. Resistance due to heat transfer
   • D. Resistance due to fluid flow

3. 39. What is 'internal diffusion resistance'?

   • A. Resistance to mass transfer within the pores of the catalyst pellet
   • B. Resistance from the bulk fluid to the pellet surface
   • C. Resistance due to heat transfer
   • D. Resistance due to fluid flow

4. 40. What is 'pressure drop' in packed bed reactors?

   • A. The reduction in fluid pressure as it flows through the packed bed
   • B. The increase in fluid pressure
   • C. The temperature change
   • D. The reaction rate

5. 41. What is the 'Ergun equation' used for?

   • A. To calculate pressure drop in packed beds
   • B. To calculate reaction rates
   • C. To calculate heat transfer coefficients
   • D. To calculate mass transfer coefficients

6. 42. What is an 'adiabatic reactor'?

   • A. A reactor where no heat is exchanged with the surroundings
   • B. A reactor where temperature is constant
   • C. A reactor where heat is continuously added
   • D. A reactor where heat is continuously removed

7. 43. What is an 'isothermal reactor'?

   • A. A reactor where the temperature is maintained constant
   • B. A reactor where no heat exchange occurs
   • C. A reactor where temperature changes
   • D. A reactor that operates at very high temperatures

8. 44. What is the concept of 'multiple steady states' in reactors?

   • A. The ability of a reactor to operate at more than one stable set of conditions for a given set of inputs
   • B. The ability of a reactor to switch between different reaction pathways
   • C. The ability of a reactor to handle different feeds
   • D. The ability of a reactor to operate without control

9. 45. What is 'catalyst deactivation'?

   • A. The loss of catalytic activity over time
   • B. The activation of a catalyst
   • C. The regeneration of a catalyst
   • D. The formation of new catalyst particles

10. 46. What is 'poisoning' of a catalyst?

    • A. Irreversible adsorption of impurities on active sites
    • B. Reversible adsorption of reactants
    • C. Physical deposition of carbon
    • D. Thermal degradation

11. 47. What is 'fouling' (or coking) of a catalyst?

    • A. Deposition of carbonaceous material on the catalyst surface
    • B. Irreversible adsorption of impurities
    • C. Thermal degradation
    • D. Physical breaking of catalyst particles

12. 48. What is 'sintering' of a catalyst?

    • A. Loss of catalyst surface area due to high temperature and agglomeration of active sites
    • B. Physical breaking of catalyst particles
    • C. Deposition of impurities
    • D. Chemical reaction with impurities