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

Related Mcqs:

1. ‘N’ plug flow reactors in series with a total volume ‘V’ gives the same conversion as a single plug flow reactor of volume ‘V’ for _______________ order reactions?

   A. First
   B. Second
   C. Third
   D. Any

2. 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

3. A reversible liquid phase endothermic reaction is to be carried out in a plug flow reactor. For minimum reactor volume, it should be operated such that the temperature along the length ?

   A. Decreases
   B. Increases
   C. Is at the highest allowable temperature throughout
   D. First increases and then decreases

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. For identical flow rate and feed composition, X plug flow reactors (PER) in series with a total volume V gives the same conversion as single_______________?

   A. CSTR of volume V
   B. PFR of volume V
   C. CSTR of volume V/X
   D. PFR of volume V/X

6. For identical flow rate, feed composition and for elementary first order reactions, ‘N’ equal sized mixed reactors in series with a total volume ‘V’ gives the same conversion as a single plug flow reactor of volume ‘V’ for constant density systems. This is true, when the value of ‘N’ is ___________________?

   A. 1
   B. > 1
   C. ∞
   D. ≥ 1

7. With increase in the order of reaction (for all positive reaction orders), the ratio of the volume of mixed reactor to the volume of plug flow reactor (for identical feed composition, flow rate and conversion)?

   A. Increases
   B. Decreases
   C. Remain same
   D. Increases linearly

8. A second order liquid phase reaction, A → B, is carried out in a mixed flow reactor operated in semi batch mode (no exit stream). The reactant A at concentration CAF is fed to the reactor at a volumetric flow rate of F. The volume of the reacting mixture is V and the density of the liquid mixture is constant. The mass balance for A is_______________________?

   A. d(VCA)/dt = -F (CAF – CA) – kCA2V
   B. d(VCA)/dt = F (CAF – CA) – kCA2V
   C. d(VCA)/dt = -FCA – kCA2V
   D. d(VCA)/dt = FCAF – kCA2V

9. A pollutant P degrades according to first order kinetics. An aqueous stream containing P at 2 kmole/m3 and volumetric flow rate 1m3 /h requires a mixed flow reactor of volume V to bring down the pollutant level to 0.5 kmole/m3. The inlet concentration of the pollutant is now doubled and the volumetric flow rate is tripled. If the pollutant level is to be brought down to the same level of 0.5 k.mole/m3, the volume of the mixed flow reactor should be increased by a factor of_______________?

   A. 7
   B. 6
   C. 3
   D. 7/3

10. The size of plug flow reactor (PFR) for all positive reaction orders and for any given duty, is _____________________ that of mixed reactor?

    A. Greater than
    B. Equal to
    C. Smaller than
    D. Unpredictable from the data