Reaction Engineering (Set 1)

Question 1

Which of the following will give maximum gas conversion?

Answer 1

Semi-fluidised bed reactor.

Question 2

____ explains the mechanism of catalysis.

Answer 2

Activated complex theory

Question 3

From among the following, choose one which is not an exothermic process.

Answer 3

Catalytic cracking

Question 4

The fractional volume change of the system for the isothermal gas phase reaction, A 3B , between no conversion and complete conversion is

Answer 4

2

Question 5

A catalyst

Answer 5

lowers the activation energy of reacting molecules.

Question 6

What is the order of a chemical reaction, A + 2B (K)→ C, if the rate of formation of ‘C’, increases by a factor of 2.82 on doubling the concentration of ‘A’ and increases by a factor of 9 on trebling the concentration of ‘B’?

Answer 6

7/2

Question 7

For high conversion in a highly exothermic solid catalysed reaction, use a ____ bed reactor.

Answer 7

fluidised bed reactor followed by a fixed

Question 8

For every 10°C rise in temperature, the rate of chemical reaction doubles. When the temperature is increased from 30 to 70°C, the rate of reaction increases ____ times.

Answer 8

16

Question 9

The single parameter model proposed for describing non-ideal flow is the ____ model.

a. tank in series
b. dispersion

Answer 9

both (a) & (b)

Question 10

A first order reaction requires two equal sized CSTR. The conversion is

Answer 10

more when they are connected in series.

Question 11

In case of physical adsorption, the heat of adsorption is of the order of ____ kcal/kg.mole.

Answer 11

1000

Question 12

The most unsuitable reactor for carrying out reactions in which high reactant concentration favours high yields is

Answer 12

backmix reactor

Question 13

Pick out the wrong statement pertaining to space velocity of flow reactors.

a. The unit of space velocity is (time)-1 .
b. The space velocity of 3 hr-1 means that three reactor volumes of feed at specified conditions are being fed into the reactor every hour.
c. The space velocity of 3 hr-1 means that one third reactor volume of feed at specified conditions are being fed into the reactor.

Answer 13

The space velocity of 3 hr-1 means that one third reactor volume of feed at specified conditions are being fed into the reactor.

Question 14

A reactor is generally termed as an autoclave, when it is a

Answer 14

high pressure batch reactor.

Question 15

6 gm of carbon is burnt with an amount of air containing 18 gm oxygen. The product contains 16.5 gms CO2 and 2.8 gms CO besides other constituents. What is the degree of conversion on the basis of disappearance of limiting reactant ?

Answer 15

0.95

Question 16

The rate constant of a chemical reaction decreases by decreasing the

Answer 16

temperature

Question 17

Reaction rate equation for the reaction, https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/448-153-1.png . If S at is present in large excess, what is the order of this reaction?

Answer 17

one

Question 18

Rate of a gaseous phase reaction is given by, https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/460-311-1.png . The unit of rate constant is

Answer 18

(atm)-1.(hr)-1

Question 19

____ is the response curve for a step input signal from a reactor.

Answer 19

S-curve

Question 20

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

Answer 20

temperature

Question 21

Which of the following is the most suitable for very high pressure gas phase reaction ?

Answer 21

Tubular flow reactor

Question 22

The reaction between oxygen and organic material is a/an ____ reaction.

Answer 22

exothermic

Question 23

With decrease in temperature, the equilibrium conversion of a reversible endother-mic reaction

Answer 23

decreases

Question 24

In an exothermic chemical reaction, the reactants compared to the products have

Answer 24

more energy

Question 25

For a reaction of the type, https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/458-286-1.png , the rate of reaction (- rx) is given by

Answer 25

K1CV - K2CX

Question 26

In a consecutive reaction system https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/446-134-1.png when E1 is much greater than E2, the yield of B increases with the

Answer 26

increase of temperature.

Question 27

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

Answer 27

is at the highest allowable temperature throughout.

Question 28

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

Answer 28

9210°K

Question 29

A batch reactor is suitable for

Answer 29

liquid phase reactions.

Question 30

For a heterogeneous catalytic reaction

Answer 30

free energy of activation is lowered in the presence of catalyst, which remains unchanged at the end of reaction.

Question 31

The increase in the rate of reaction with temperature is due to

Answer 31

decrease in activation energy.

Question 32

A catalyst loses its activity due to a. loss in surface area of the active component. b. agglomeration of metal particles caused by thermal sintering of the solid surface. c. covering of the catalytic active sites by a foregin substance.

Answer 32

all (a), (b) and (c).

Question 33

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.

Answer 33

any

Question 34

Specific rate constant for a second order reaction a. is independent of temperature. b. varies with temperature. c. depends on the nature of the reactants.

Answer 34

both (b) and (c).

Question 35

For the irreversible elementary reactions in parallel viz https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/455-247-1.png , the rate of disappearance of 'X' is equal to

Answer 35

CA(K1+K2)

Question 36

For an isothermal variable volume batch reactor, the following relation is applicable for a first order irreversible reaction.

Answer 36

CAo/(1+εAXA)(dXA/dt) = k

Question 37

For a zero order chemical reaction, the

Answer 37

all (a), (b) and (c).

Question 38

BET apparatus a. measures the catalyst surface area directly. b. operates at very high pressure. c. is made entirely of stainless steel.

Answer 38

none of these.

Question 39

Radioactive decay follows ____ order kinetics.

Answer 39

first

Question 40

The excess energy of reactants in a chemical reaction required to dissociate into products is termed as the ____ energy.

Answer 40

activation

Question 41

For a solid catalysed chemical reaction, the effectiveness of solid catalyst depends upon the ____ adsorption.

Answer 41

chemical

Question 42

Pick out the correct statement. a. In catalytic reactions, the catalyst reacts with the reactants. b. A catalyst initiates a chemical reaction. c. A catalyst lowers the activation energy of the reacting molecules. d. A catalyst can not be recovered chemi cally unchanged at the end of the chemical reaction.

Answer 42

A catalyst lowers the activation energy of the reacting molecules.

Question 43

The dimensions of rate constant for reaction 3A --> B are (l/gm mole)/min. Therefore the reaction order is

Answer 43

2

Question 44

Pick out the correct statement

Answer 44

Reactions with high activation energies are very temperature sensitive.

Question 45

If the time required to complete a definite fraction of reaction varies inversely as the concentration of the reactants, then the order of reaction is

Answer 45

2

Question 46

Sulphuric acid is used as a catalyst in the

Answer 46

alkylation of hydrocarbons.

Question 47

Fractional conversion ____ with increase in pressure for ammonia synthesis reaction i.e., N2 + 3H2 <->2NH3.

Answer 47

increases

Question 48

Pick out the wrong statement. a. The vessel dispersion number (D/UL) for plug flow and mixed flow approaches zero and infinity respectively. b. Space time in a flow reactor is a measure of its capacity and is equal to the residence time when the density of reaction mixture is constant. c. Mixed reactor is always smaller than the plug flow reactor for all positive reaction orders for a particular duty. d. In an ideal tubular flow reactor, mixing takes place in radial direction and there is no mixing in logitudinal direction.

Answer 48

Mixed reactor is always smaller than the plug flow reactor for all positive reaction orders for a particular duty.

Question 49

The reason why a catalyst increases the rate of reaction is that, it

Answer 49

decreases the energy barrier for reaction.

Question 50

A first order irreversible reaction, A --> B is carried out separately in a constant volume as well as in a variable volume reactor for a particular period. It signifies that ____ in the two reactors.

Answer 50

conversion in both will be the same but concentrations will be different

Question 51

When the density of the reaction mixture is constant in a chemical reaction, the ratio of the mean residence time to space time is

Answer 51

1

Question 52

In an ideal tubular-flow reactor

Answer 52

all (a), (b) and (c).

Question 53

At a given value of E/R (ratio of activation energy and gas constant), the ratio of the rate constants at 500°K and 400°K is 2, if Arrhenious law is used. What will be this ratio, if transition state theory is used with the same value of E/R?

Answer 53

2.5

Question 54

____ is the controlling step in a highly temperature sensitive fluid-solid non-catalytic reaction.

Answer 54

Chemical reaction

Question 55

An autothermal reactor is

Answer 55

completely self-supporting in its thermal energy requirements.

Question 56

The rate constant of a first order reaction depends on the

Answer 56

temperature.

Question 57

A reaction in which one of the products of reaction acts as a catalyst is called a/an ____ reaction.

Answer 57

autocatalytic

Question 58

The ratio of volume of mixed reactor to the volume of P.F.R. (for identical flow rate, feed composition and conversion) for zero order reaction is

Answer 58

1

Question 59

Which of the following will favour the reverse reaction in a chemical equilibrium reaction ? a. Increasing the concentration of one of the reactants. b. Increasing the concentration of one or more of the products. c. Removal of at least one of the products at regular interval.

Answer 59

Increasing the concentration of one or more of the products.

Question 60

Conversion increases with increase in temperature in case of a an ____ reaction.

Answer 60

reversible endothermic

Question 61

Effective diffusivity (DE) in a catalyst pellet is related to molecular diffusivity (DN) and Knudsen diffusivity (DK) as

Answer 61

1/DE = 1/DN + 1/DK

Question 62

A photochemical reaction is ____ light.

Answer 62

initiated by

Question 63

Pick out the wrong statement. a. In a batch reactor, which is exclusively used for liquid phase reactions; temperature pressure and composition may vary with time. b. In a semi-batch reactor, one reactant is charged batchwise, while the other reactant is fed continuously. c. In a continuous flow reactor, uniform concentration can not be maintained throughout the vessel even in a well agitated system. d. In a continuous flow reactor, both the reactants and the products flow out continuously.

Answer 63

In a continuous flow reactor, uniform concentration can not be maintained throughout the vessel even in a well agitated system.

Question 64

In a/an ____ reactor, there is exchange of heat with the surroundings with sizeable temperature variation.

Answer 64

non-adiabatic

Question 65

Unreacted core model' represents the reaction involving

Answer 65

roasting of sulphide ores.

Question 66

For a vapour phase catalytic reaction (A + B --> P) which follows the Ridel mechanism and the reaction step is rate controlling, the rate of reaction is given by (reaction rate is irreversible, product also absorbs).

Answer 66

https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/475-472-1.png

Question 67

If a solid-gas non-catalytic reaction occurs at very high temperature, the rate controlling step is the ____ diffusion.

Answer 67

film

Question 68

The units of frequency factor in Arhenious equation

Answer 68

are the same as those of the rate constant.

Question 69

Which of the following is not a chemical step in a fluid solid catalytic reaction ?

Answer 69

None of these

Question 70

For a series of reactions https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/473-457-1.png having k1 << k2, the reaction system can be approximated as

Answer 70

https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/476-478-1u.png

Question 71

At a given temperature, K1, K2 and K3 are equilibrium constants for the following reactions 1, 2, 3 respectively. CH4(g) + H2O(g) CO(g) + 3H2(g), CO(g) + H2O(g) CO2(g) + H2(g) CH4(g) + 2H2O(g) CO2(g) + 4H2(g) Then K1, K2 and K3 are related as:

Answer 71

K3 = K1.K2

Question 72

In case of ____ reactions, the reaction rate does not decrease appreciably as the reaction proceeds.

Answer 72

auto catalytic

Question 73

For nearly isothermal operation involving large reaction time in a liquid-phase reaction, the most suitable reactor is a ____ reactor.

Answer 73

stirred tank

Question 74

What is the Thiele modulus of the solid catalysed first order reaction, https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/448-154-1.png , if the pore diffusion offers negligible resistance to reaction ?

Answer 74

< 0.5

Question 75

B.E.T. method can be used to determine the ____ of a porous catalyst.

Answer 75

surface area

Question 76

Rate constant for a first order reaction does not depend upon reaction time, extent of reaction and the initial concentration of reactants ; but it is a function of reaction temperature. In a chemical reaction, the time required to reduce the concentration of reactant from 100 gm moles/litre to 50 gm moles/litre is same as that required to reduce it from 2 gm moles/litre to 1 gm mole/litre in the same volume. Then the order of this reaction is

Answer 76

1

Question 77

Which of the following is an independent variable for a batch tank reactor with uniform concentration and temperature?

Answer 77

Time

Question 78

For reactions in parallel viz A -->P (desired product) and A-->Q (unwanted product), if the order of the desired reaction is higher than that of the undesired reaction, a

Answer 78

both (a) and (b).

Question 79

For a gaseous phase reaction, rate of reaction is equal to K. CA . CB. If the volume of the reactor is suddenly reduced to l/4th of its initial volume, then the rate of reaction compared to the original rate will be ____ times.

Answer 79

16

Question 80

In a reversible chemical reaction having two reactants in equilibrium, if the concentration of the reactants are doubled, then the equilibrium constant will

Answer 80

remain the same

Question 81

The equilibrium constant of a catalytic chemical reaction ____ due to the presence of a catalyst.

Answer 81

remains unaffected

Question 82

The rate constant of a chemical reaction increases by increasing the

Answer 82

temperature

Question 83

The catalytic activity of enzymes is due to their capacity to lower the ____ energy.

Answer 83

activation

Question 84

A first order reaction requires two unequal sized CSTR. Which of the following gives higher yield ?

Answer 84

Either of the arrangement (a) or (b) will give the same yield.

Question 85

Pick out the correct statement.

Answer 85

A lower temperature favours the reaction of lower activation energy.

Question 86

The effect of increasing pressure on the gaseous equilibrium of the reaction 2X+3Y <-->3X+2Y indicates that

Answer 86

pressure has no effect.

Question 87

If in the gaseous phase reaction, N2O4 <--> 2NO2, x is the part of N2O4 which dissociates, then the number of molecules at equilibrium will be

Answer 87

(1 + x)

Question 88

A batch reactor is characterised by

Answer 88

variation in extent of reaction and properties of the reaction mixture with time.

Question 89

When a catalyst increases the rate of forward reaction, the value of rate constant

Answer 89

increases

Question 90

Rate determining step in a reaction consisting of a number of steps in series is the ____ step.

Answer 90

slowest

Question 91

The rate of a chemical reaction is almost doubled for every 10°C rise in temperature. The rate will increase ____ times, if the temperature rises form 10 to 100°C.

Answer 91

512

Question 92

A catalyst in a chemical reaction ____ free energy change in the reaction. a. increases b. decreases

Answer 92

either (a) or (b); depends on the type of catalyst

Question 93

Signal normally used to study non-ideal flow by stimulus response technique is ____ input. a. pulse b. step

Answer 93

both (a) & (b)

Question 94

When all the limiting reactant is consumed in the reaction, the operational yield ____ the relative yield.

Answer 94

equals

Question 95

The half life period of a first order reaction is

Answer 95

independent on initial concentration of the reactants.

Question 96

The catalyst in a second order reversible reaction increases the rate of the forward reaction

Answer 96

and backward reaction equally.

Question 97

Catalyst carriers

Answer 97

provide large surface area with a small amount of active material.

Question 98

For the liquid phase zero order irreversible reaction A--> B, the conversion of A in a CSTR is found to be 0.3 at a space velocity of 0.1min-1 . What will be the conversion for a PFR with a space velocity of 0.2 min-1? Assume that all the other operating conditions are the same for CSTR and PFR.

Answer 98

0.6

Question 99

A high space velocity means that a given a. reaction can be accomplished with small reactor. b. conversion can be obtained with a high feed rate.

Answer 99

both (a) and (b).

Question 100

In flow reactors, the performance equations interrelate the rate of reaction to the

Answer 100

all (a), (b) and (c).