Reaction Engineering (Set 4)

Question 1

The minimum energy required to allow a chemical reaction to proceed is termed as the ‘threshold energy ‘. Chemical reaction with low activation energy are

Answer 1

insensitive to temperature changes.

Question 2

If Thiele modulus is ____ , then the pore diffusion resistance in a catalyst may be considered as negligible.

Answer 2

< 0.5

Question 3

From collison theory, the reaction rate constant is proportional to

Answer 3

T^rn.exp(-E/RT)

Question 4

For a mixed flow reactor operating at steady state, the rate of reaction is given by

Answer 4

FAo/V . XA

Question 5

Catalytic action in a catalytic chemical reaction follows from the ability of catalyst to change the

Answer 5

activation energy

Question 6

In Langmuir treatment of adsorption,

Answer 6

whole surface of the catalyst is essentially uniform and the adsorbed molecule has no effect on the rate of adsorption per site.

Question 7

Organic catalysts differ from the inorganic catalyst in the sense that the former is

Answer 7

proteinous in nature.

Question 8

An endothermic aqueous phase first order irreversible reaction is carried out in an adiabatic plug flow reactor. The rate of reaction

Answer 8

is maximum at the inlet of the reactor.

Question 9

Pick out the wrong statement.

Answer 9

A catalyst increases the potential energy barrier over which the reactants must pass to form products.

Question 10

For an ideal plug flow reactor, the value of Peclet number is

Answer 10

0

Question 11

An endothermic second order reaction is carried out in an adiabatic plug flow reactor. The rate of heat generation is

Answer 11

maximum at the inlet of the reactor.

Question 12

Equilibrium of a chemical reaction as viewed by kinetics is a ____ state.

Answer 12

dynamic steady

Question 13

The conversion in a mixed reactor/accomplishing a reaction A –>3R is 50% when gaseous reactant ‘A’ is introduced at the rate of 1 litre/second and the leaving flow rate is 2 litres/second. The holding time for this operation is ____ second.

Answer 13

0.5

Question 14

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

Answer 14

smaller than

Question 15

A space time of 3 hours for a flow reactor means that

Answer 15

the time required to process one reactor volume of feed (measured at specified conditions) is 3 hours.

Question 16

If the time required for half change is inversely proportional to the square of initial concentration and the velocity depends on the units in which the concentration term is expressed, then the order of reaction is

Answer 16

3

Question 17

The experimentally determined overall order of the reaction, A + B –> C + D, is two. Then the

Answer 17

reaction is elementary with a molecularity of 2.

Question 18

In a continuous flow stirred tank reactor, the composition of the exit stream

Answer 18

is same as that in the reactor.

Question 19

Recycling back of outlet stream to the reactor from an ideal CSTR carrying out a first order liquid phase reaction will result in ____ in conversion.

Answer 19

no change

Question 20

The energy balance equation over a tubular reactor under transient conditions is

Answer 20

a linear partial differential equation.

Question 21

Which of the following factors control the deactivation of a porous catalyst pellet ?

Answer 21

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

Question 22

For the reaction, A + B –>2B + C,

Answer 22

rA = -rB

Question 23

Transition state theory gives the rate constant as

Answer 23

K α T . e^-E/RT

Question 24

A liquid phase reaction is to be carried out under isothermal conditions. The reaction rate as a function of conversion has been determined experimentally and is shown in the figure given below. What choice of reactor or combination of reactors will require the minimum overall reactor volume, if a conversion of 0.9 is desired ?

Answer 24

PFR followed by a CSTR

Question 25

Pick out the wrong statement.

Answer 25

Activation energy for a reaction is obtained from the intercept of the Ar-rhenious plot.

Question 26

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

Answer 26

and the backward reaction equally.

Question 27

Maximum equilibrium conversion for endothermic reaction is obtained at the ____ temperature.

Answer 27

highest possible

Question 28

When an exothermic reversible reaction is conducted adiabatically, the rate of reaction

Answer 28

continuously decreases.

Question 29

For a first order chemical reaction in a porous catalyst, the Thiele modulus is 10. The effectiveness factor is approximately equal to

Answer 29

0.1

Question 30

The rate equation for the reaction represented by https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/455-245-1.png , is given by - rx = K1 . Cx/(1 + K2 Cx). At high value of Cx (i.e.., K2Cx > > 1), the order of the reaction and the rate constant are respectively

Answer 30

zero order & K1/K2

Question 31

In solid catalysed reactions the diffusional effects are more likely to affect the overall rate of reaction for

Answer 31

fast reaction in catalyst of large pore diameter.

Question 32

Helium-mercury method can be used to determine the ____ of the catalyst particle.

Answer 32

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

Question 33

For the chemical reaction X --> Y, it is observed that, on doubling the concentration of 'X', the reaction rate quadruples. If the reaction rate is proportional to Cxn, then what is the value of 'n' ?

Answer 33

4

Question 34

Chemical reaction rate of a component depends upon the

Answer 34

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

Question 35

In a semi-batch reactor

Answer 35

velocity of reaction can be controlled.

Question 36

A trickle bed reactor is the one, which

Answer 36

employs all the three phases (i.e.. .solid, liquid and gas).

Question 37

What is the order of a chemical reaction in which doubling the initial concentration of the reactants doubles the half life time of the reaction ?

Answer 37

0

Question 38

The excess energy of the reactants required to dissociate into products is known as the ____ energy.

Answer 38

activation

Question 39

In a/an ____ vessel, the fluid enters and leaves following plug flow.

Answer 39

closed

Question 40

Shift conversion reaction

Answer 40

converts CO to CO2 with steam.

Question 41

The importance of diffusion in a catalyst are increased by

Answer 41

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

Question 42

A back mix reactor is

Answer 42

same as ideal stirred tank reactor.

Question 43

Which one is the rate controlling step in a solid-gas non-catalytic reaction occurring at very high temperature?

Answer 43

Film diffusion

Question 44

The rate of the heterogenous catalytic reaction A(g) + B(g) -->C(g) is given by -rA = k.KA.pA.PB/(1 + KA.PA + Kc.pc), where KA and Kc are the adsorption equilibrium constants. The rate controlling step for this reaction is

Answer 44

surface reaction between absorbed A and B in the gas phase.

Question 45

For a ____ order chemical reaction, https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/449-168-1.png , the half life period is independent of the initial concentration of the reactant A.

Answer 45

first

Question 46

The ratio of moles of a reactant converted into the desired product to that converted into unwanted product is called

Answer 46

selectivity

Question 47

The response curve for a step input signal from a reactor is called C-curve. The variance of C-curve in a 'tanks in series model' comprising of 'm' tanks is equal to

Answer 47

1/m

Question 48

The eddy diffusivity for a liquid in plug flow must be

Answer 48

0

Question 49

For multiple reactions, the flow pattern within the vessel affects the

Answer 49

both (a) and (b)

Question 50

The rate expression for the gaseous phase reaction, CO + 2H2 --> CH3OH, is given by, https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/477-488-1.png . Which of the following is not possible ?

Answer 50

α = 1, β = 1, γ =1

Question 51

For the same residence time, which one will give the maximum conversion ?

Answer 51

Single tubular flow reactor (v = 5 litres).

Question 52

____ gas is normally employed in B.E.T.method of finding out the surface area of catalyst.

Answer 52

N2

Question 53

The exit age distribution curve E(t) for an ideal CSTR with the average residence time, τ, is given by

Answer 53

[(e^-t/τ)/T]

Question 54

The rate constant of a reaction depends on the

Answer 54

temperature of the system.

Question 55

For the reversible reaction A <-->2B, if the equilibrium constant K is 0.05 mole/litre; starting from initially 2 moles of A and zero moles of B, how many moles will be formed at equilibrium ?

Answer 55

0.338

Question 56

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

Answer 56

PFR of volume V

Question 57

Time required for 50% decomposition of a liquid in an isothermal batch reactor following first order kinetics is 2 minutes. The time required for 75% decomposition will be about ____ minutes.

Answer 57

4

Question 58

For a ____ order reaction, the units of rate constant and rate of reaction are the same.

Answer 58

zero

Question 59

In case of staged packed bed reactors carrying out exothermic reaction, use

Answer 59

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

Question 60

Vegetable oils are hydrogenated in a ____ reactor.

Answer 60

slurry

Question 61

Pure A in gas phase enters a reactor 50% of this A is converted to B through the reaction, A --> 3B. Mole fraction of A in the exit stream is

Answer 61

45294

Question 62

The rate of reaction does not decrease appreciably as the reaction proceeds in case of ____ reactions.

Answer 62

autocatalytic

Question 63

For all positive reaction orders for a particular duty,

Answer 63

mixed reactor is always larger than the plug-flow reactor.

Question 64

The heat of reaction

Answer 64

is independent of the mechanism of reaction.

Question 65

Which of the following does not produce a change in the value of rate constant of a reaction ?

Answer 65

Concentration and catalyst

Question 66

With increase in temperature, the equilibrium conversion of a reversible exothermic reaction

Answer 66

decreases

Question 67

In a CSTR ____ varies with time. a. reaction rate b. concentration c. both (a) & (b) d. neither (a) nor (b)

Answer 67

neither (a) nor (b)

Question 68

The following gas phase reactions are carried out isothermally in a CSTR. A --> 2R ; r1 = k1pA ; k1 = 20mole/(sec.m3 bar) A --> 3S ; r2 = k2 pA ; k2 = 40mole/(sec.m3 .bar) What is the maximum possible value of FR(mole/sec.) ?

Answer 68

45325

Question 69

As the chemical reaction proceeds, the rate of reaction

Answer 69

decreases.

Question 70

Pick out the wrong statement.

Answer 70

A catalyst initiates a reaction.

Question 71

In a first order reaction, the time required to reduce the concentration of reactant from 1 mole/litre to 0.5 mole/litre will be ____ that required to reduce it from 10 moles/litre to 5 moles/litre in the same volume.

Answer 71

same as

Question 72

Photo-chemical reactions occur in presence of

Answer 72

sunlight.

Question 73

n' number of plug flow reactors (P.F.R) in series with a total volume 'V' gives the same conversion as one P.F.R. of volume

Answer 73

V

Question 74

Knudsen diffusion is directly proportional to

Answer 74

sqrt(T)

Question 75

Fractional conversion ____ for an exothermic reversible chemical reaction, when the temperature is maximum.

Answer 75

decreases

Question 76

Non-catalytic fluid-solid reactions are represented by ____ model.

Answer 76

both (a) and (b) ## Footnote continuous reaction & unreacted core

Question 77

A pulse tracer is introduced in an ideal CSTR (with a mean residence time ι) at time, t = 0. The time taken for the exit concentration of the tracer to reach half of its initial value will be

Answer 77

2τ

Question 78

On application of pressure to the equilibrium system, ice <--> water ; which of the following phenomenon will occur ?

Answer 78

More water will be formed.

Question 79

Participation of ____ is involved in the occurrence of a chemical reaction.

Answer 79

electrons

Question 80

Promoter.

Answer 80

increases the number of active centres by increasing the unevenness of catalyst surface and by creating discontinuities in the crystals.

Question 81

The rate constant of a reaction is a function of the

Answer 81

temperature of the system.

Question 82

Mean residence time is equal to the space time, when

Answer 82

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

Question 83

If 'n' is the order of reaction, then unit of rate constant is

Answer 83

1/(time)(concentration)^n - 1

Question 84

Batch process is preferred over continuous process, when the

Answer 84

all (a), (b) & (c)

Question 85

The value of 'n' for a chemical reaction A --> B, whose reaction rate is -->CAn, will be ____ if the rate of the reaction increases by a factor of 8, when the concentration of is doubled.

Answer 85

3

Question 86

With the same reaction time, initial concentration and feed rate, the reaction 2A -->B is carried out separately in CSTR and P.F. reactor of equal volumes. The conversion will be

Answer 86

higher in P.F. reactor

Question 87

For any reaction, we may write conversion as a function of

Answer 87

all (a), (b) & (c)

Question 88

The use of space time is preferred over the mean residence time in the design of a/an

Answer 88

ideal tubular-flow reactor

Question 89

Autocatalytic reactions are best carried out in a

Answer 89

recycle reactor

Question 90

The gas phase reaction 2A <--> B is carried out in an isothermal plug flow reactor. The feed consists of 80 mole % A and 20 mole % inerts. If the conversion of A at the reactor exit is 50%, then CA/CA0 at the outlet of the reactor is

Answer 90

45420

Question 91

A batch reactor suffers from following disadvantage.

Answer 91

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

Question 92

A first order reaction is to be treated in a series of two mixed reactors. The total volume of the two reactors is minimum, when the reactors are

Answer 92

equal in size.

Question 93

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

Answer 93

https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/479-499-4.png

Question 94

Half life period of a chemical reaction is proportional to CA0-1 , if the reaction is of ____ order.

Answer 94

second

Question 95

The irreversible reaction, X --> Y, is the special case of the reversible reaction, X <-->Y, in which the

Answer 95

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

Question 96

The equilibrium constant K of a chemical reaction depends on

Answer 96

temperature only.

Question 97

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

Answer 97

fraction of molecules having threshold energy increases.

Question 98

Which of the following is not a unit of reaction rate ?

Answer 98

None of these

Question 99

Brunaur, Emmet and Teller (BET) equation is used to determine the specific surface area of a porous particle but not the pore volume & the porosity of the catalyst bed. Which of the following postulates is not used to derive BET equation ?

Answer 99

There is no dynamic equilibrium between successive layer.

Question 100

The sequence in which three CSTR's of volumes 5, 10 and 15 m3 will be connected in series to obtain the maximum production in a second order irreversible reaction is

Answer 100

15, 10, 5