Thursday, February 25, 2021

GATE Chemical Engineering Questions and Answers – Chemical Reaction Engineering

The rate constant of a chemical reaction increases by 100 times when the temperature is increased from 400 K to 500 K. Assuming Transition state theory is valid, the value of E/R is

(A)          8987 K

(B)           9210 K

(C)           8764 K

(D)          8621 K

                                                                                                            GATE 1995

Answer:          (C)

 

The dimensions of rate constant for reaction 3A → B are lit/(g.mol.min). Therefore the reaction order is

(A)          0

(B)           1

(C)           2

(D)          3

                                                                                                            GATE 1995

Answer:          (C)

 

A first order reaction A → B occurs in an isothermal porous catalyst pellet of spherical shape. If the concentration of A at the centre of the pellet is much less than that at the external surface, the process is limited by

(A)          Diffusion within the pellet

(B)           Reaction

(C)           External mass transfer

(D)          None of the above

                                                                                                            GATE 1995

Answer:          (A)

 

To maximize the formation of R in the simultaneous reactions

GATE 1994

We should have

(A)          Low CA, low CB

(B)           Low CA, high CB

(C)           High CA, low CB

(D)          High CA, high CB

                                                                                                            GATE 1994

Answer:          (B)

 

For the gaseous reaction 2A → B where the feed consists of 50 mole% A and 50 mole% inerts, the expansion factor is

(A)          1

(B)           -0.5

(C)           -0.25

(D)          0

                                                                                                            GATE 1994

Answer:          (C)

 

The conversion of a reactant undergoing a first order reaction at a time equal to three times the half life of the reaction is

(A)          0.875

(B)           0.50

(C)           0.425

(D)          Not impossible to calculate because of insufficient data

                                                                                                            GATE 1992

Answer:          (A)

 

A gaseous reaction A → 2B + C takes place isothermally in a constant pressure reactor. Starting with a gaseous mixture containing 50% A (rest inerts), the ratio of final to initial volume is found to be 1.6. the percentage conversion of A is

(A)          30

(B)           50

(C)           60

(D)          74

                                                                                                            GATE 1992

Answer:          (C)

 

The unit of frequency factor in Arrhenius equation

(A)          Are the same as those of the rate constant

(B)           Depend on the order of the reaction

(C)           Depend on the temperature, pressure, etc of the reaction

(D)          Are cycles per unit time

                                                                                                            GATE 1992

Answer:          (A)

 

Thiele modulus is defined as

(A)          D/K

(B)           K/D

(C)           L(K/D)0.5

(D)          LK/D

                                                                                                            GATE 1991

Answer:          (C)

 

The reaction between A and B produces the desired product R as well as the unwanted product S. what level of reactant concentration (high, medium, low) should we use for the following reaction scheme in order to maximize the conversion of A to R.

Reaction scheme:

GATE 1991

(A)          Low CA, low CB

(B)           High CB, any CA

(C)           High CA, low CB

(D)          High CA, any CB

                                                                                                            GATE 1991

Answer:          (B)

 

The rate of a liquid phase reaction of the type A + B → P is found to be independent of concentration of A and B and equal to 1 kmol/m3.min at 300 K. Find the conversion in a mixed flow reactor having volume equal to 2 m3 with feed concentration of A and b equal to 5 kmol/m3, feed flow rate equal to 1 m3/min and the reactor temperature equal to 300 K.

(A)       0.4

(B)        0.5

(C)        0.6

(D)       0.7

                                                                                                            GATE 1991

Answer:          (A)

 

For an elementary reaction A + B → products, the reaction rate at 500 K is ten times that at 400 K. Calculate the activation energy for this reaction

(A)          38.29 KJ/g.mol

(B)           42.25 KJ/g.mol

(C)           46.25 KJ/g.mol

(D)          48.35 KJ/g.mol

                                                                                                            GATE 1990

Answer:          (A)

 

What is the exit conversion of reactant A for a zero order reaction taking place in a CSTR with the following data (rate constant = 1 mol/min.lit, feed concentration = 1 mole/lit, feed flow rate = 0.5 lit/min and reactor volume = 1 lit)

(A)          50%

(B)           75%

(C)           100%

(D)          200%

                                                                                                            GATE 1990

Answer:          (D)

 

An exothermic gas phase reaction proceeds according to the equation 3A + 2D  2R. The equilibrium conversion for this reaction

(A)          Increases with increase in temperature

(B)           Decreases on dilution with an inert gas

(C)           Decreases with an increase in pressure

(D)          Is unbaffled by the presence of a catalyst

                                                                                                            GATE 1990

Answer:          (D)

 

In a homogeneous gas phase reaction A + 2B → R + S. What is the relationship between rA and rB?

(A)          2rA = rB

(B)           rA = 2rB

(C)           rA = rB

(D)          none of these

                                                                                                            GATE 1990

Answer:          (A)

 

For the following reaction, the rate constant at 373 K is 0.5 per min 0.5 A + B → C. The overall order of reaction is

(A)          0.5

(B)           1.0

(C)           1.5

(D)          0

                                                                                                            GATE 1989

Answer:          (B)

 

From the stoichiometry, one can say that the following reaction is non-elementary

N2 + 3H2 → 2NH3

The reason is

(A)          No elementary reaction has an order greater than 2

(B)           The order of the forward reaction is not the same as that of the backward reaction

(C)           The reaction takes place in gas phase only

(D)          None of these

                                                                                                            GATE 1989

Answer:          (A)

 

In transition state theory the rate of the reaction is derived by assuming that the activated complex in equilibrium with

(A)          The products

(B)           The reactants

(C)           Both reactants and products

(D)          None of the above

                                                                                                            GATE 1988

Answer:          (B)

 

Liquid A decomposes by first order kinetics in an isothermal batch reactor. 50% of A is converted in 300 seconds. The time required for a conversion of 75% is

(A)          300 × 0.75/0.25 sec

(B)           300 ln 1 sec

(C)           300 ln(0.5/0.25) sec

(D)          300 {(ln0.25)/(ln0.5)}

                                                                                                            GATE 1988

Answer:          (D)

 

The reaction A → B occurs in an isothermal catalyst pellet under steady state conditions. If the diffusion of A into the pellet is the rate controlling steps, the rate of diffusion of A is

(A)          Faster than the rate of reaction

(B)           Equal to the rate of reaction

(C)           Slower than the rate of reaction

(D)          May be faster or slower depending on the kinetics

                                                                                                            GATE 1988

            Answer:          (C)

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