Chemical Reaction Engineering MCQs

Question 1

For a first order isothermal chemical reaction in a porous catalyst, the effectiveness factor is 0.3. The effectiveness factor will increase if the

Accepted Answer

Catalyst size is reduced or the catalyst diffusivity is increased

Answer

Catalyst size is reduced or the catalyst diffusivity is reduced

Answer

Catalyst size is increased or the catalyst diffusivity is reduced

Answer

Catalyst size is increased or the catalyst diffusivity is increased

Question 2

Pick out the wrong statement.

Accepted Answer

For a first order consecutive reaction, a tubular flow reactor as compared to a stirred tank reactor provides higher overall selectivity

Answer

For an ideal mixed reactor at steady state, the exit stream has the same composition as fluid within the reactor and the space time is equivalent to holding time for constant density system

Answer

Plug flow reactor (PFR) is always smaller than mixed reactor for all positive reaction orders for a particular duty

Answer

Reaction rate does not decrease appreciably as the reaction proceeds in case of an autocatalytic reaction

Question 3

A batch reactor suffers from following disadvantage.

Accepted Answer

All of the above

Answer

Poor product quality control

Answer

High labour and handling cost

Answer

High shutdown time requirement for emptying, cleaning and refilling

Question 4

The reaction rate almost gets doubled for 10°C rise in temperature. This is due to the fact that the

Accepted Answer

Fraction of molecules having threshold energy increases

Answer

Increased temperature reduces the activation energy

Answer

Collision frequency increases

Answer

Value of threshold energy decreases

Question 5

In a zero order reaction, reactants concentration does not change with time and the

Accepted Answer

Time for half change is half the time taken for completion of the reaction

Answer

Time for half change is independent of the initial concentration

Answer

Time for completion of the reaction is independent of the initial concentration

Answer

Reaction rate is trebled when the initial concentration is trebled

Question 6

Pick out the wrong statement.

Accepted Answer

Hydrolysis of ester in presence of alkali or acid is a zero order reaction

Answer

Autocatalytic reactions are exemplified by microbial fermentation reactions

Answer

The slowest step has the greatest influence on the overall reaction rate in case of an irreversible series reaction

Answer

The fractional conversion at any time is same for both the constant as well as the variable volume system in case of an irreversible unimolecular type first order reaction

Question 7

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 $$\frac{7}{8}$$. Which of the following statement is true?

Accepted Answer

Inner catalyst core of radius $$\frac{{	ext{R}}}{8}$$ does not participate in reaction

Answer

Inner catalyst core of radius $$\frac{{	ext{R}}}{2}$$ does not participate in reaction

Answer

Inner catalyst core of radius $$\frac{{7{	ext{R}}}}{8}$$ does not participate in reaction

Answer

Effectiveness factor for a zero order reaction can not be $$\frac{7}{8}$$ as it must always be 1

Question 8

For series reaction, the relative yield

Accepted Answer

Both A and C hold good

Answer

Is always greater for plug-flow reactor than for the single CSTR of the same volume

Answer

Statement in A is wrong

Answer

Decreases with increasing conversion

Question 9

In a reversible reaction, a catalyst increases the rate of forward reaction

Accepted Answer

And the backward reaction equally

Answer

Only

Answer

To a greater extent than that of the backward reaction

Answer

And decreases that of the backward reaction