CRE Flashcards
1
Q
Which of the following will give maximum gas conversion?
A. Fixed bed reactor.
B. Fluidized bed reactor.
C. Semi-fluidized bed reactor.
D. Plug-flow catalytic reactor.
A
Semi-fluidised bed reactor.
2
Q
__________ explains the mechanism of catalysis.
A
Activated complex theory
3
Q
From among the following, choose one which is not an exothermic process.
A. Methanol synthesis
B. Catalytic cracking
C. Ammonia synthesis
D. Oxidation of sulphur
A
Catalytic cracking
4
Q
The fractional volume change of the system for the isothermal gas phase reaction, A 3B , between no conversion and complete conversion is
A
2
5
Q
A catalyst
A. initiates a reaction.
B. lowers the activation energy of reacting molecules.
C. is capable of reacting with any one of the reactants.
D. cannot be recovered chemically unchanged at the end of a chemical reaction.
A
lowers the activation energy of reacting molecules.
6
Q
What is the order of a chemical reaction, A + 2B –> 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’?
A
7/2
7
Q
For high conversion in a highly exothermic solid catalysed reaction, use a __________ bed reactor.
A
fluidised bed reactor followed by a fixed
8
Q
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.
A
16
9
Q
A first order reaction requires two equal sized CSTR. The conversion is
A
more when they are connected in series.
10
Q
In case of physical adsorption, the heat of adsorption is of the order of __________ kcal/kg.mole.
A
1000
11
Q
The most unsuitable reactor for carrying out reactions in which high reactant concentration favours high yields is
A
backmix reactor
12
Q
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.
D. none of these.
A
The space velocity of 3 hr-1 means that one third reactor volume of feed at specified conditions are being fed into the reactor.
13
Q
A reactor is generally termed as an autoclave, when it is a
A
high pressure batch reactor.
14
Q
6 kg 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 ?
A
0.95
15
Q
The rate constant of a chemical reaction decreases by decreasing the
A
temperature
16
Q
Reaction rate equation for the reaction, R + 2S -> X + Y is -dCR/dt = KCRCS^2 . If S at is present in large excess, what is the order of this reaction?
A
one
17
Q
Rate of a gaseous phase reaction is given by, -dpA/dt = KpA^2 . The unit of rate constant is
A
(atm)-1.(hr)-1
18
Q
__________ is the response curve for a step input signal from a reactor.
A
S-curve
19
Q
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
temperature
20
Q
Which of the following is the most suitable for very high pressure gas phase reaction ?
A. Batch reactor
B. Tubular flow reactor
C. Stirred tank reactor
D. Fluidized bed reactor
A
Tubular flow reactor
21
Q
The reaction between oxygen and organic material is a/an __________ reaction.
A
exothermic
22
Q
With decrease in temperature, the equilibrium conversion of a reversible endother-mic reaction
A
decreases
23
Q
In an exothermic chemical reaction, the reactants compared to the products have
A
more energy
24
Q
For a reaction of the type, V —k1–> X –k2–> Y –k3–> Z , the rate of reaction (- rx) is given by
A
K1CV - K2CX
25
In a consecutive reaction system A --E1--> B --E2--> C when E1 is much greater than E2, the yield of B increases with the
increase of temperature.
26
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
is at the highest allowable temperature throughout.
27
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
9210°K
28
A batch reactor is suitable for
liquid phase reactions.
29
For a heterogeneous catalytic reaction
free energy of activation is lowered in the presence of catalyst, which remains unchanged at the end of reaction.
30
The increase in the rate of reaction with temperature is due to
decrease in activation energy.
31
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 foreign substance.
D. all (a), (b) and (c).
all (a), (b) and (c).
32
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.
any
33
For an isothermal variable volume batch reactor, the following relation is applicable for a first order irreversible reaction.
CAo/(1+εAXA)(dXA/dt) = k
34
For a zero order chemical reaction, the
A. half life period is directly proportion to the initial concentration of the reactants.
B. plot of products concentration with time is a straight line through the origin.
C. products concentration increases linearly with time.
D. all (a), (b) and (c).
all (a), (b) and (c).
35
BET apparatus
A. measures the catalyst surface area directly.
B. operates at very high pressure.
C. is made entirely of stainless steel.
D. none of these.
none of these.
36
Radioactive decay follows __________ order kinetics.
first
37
The excess energy of reactants in a chemical reaction required to dissociate into products is termed as the __________ energy.
activation
38
For a solid catalysed chemical reaction, the effectiveness of solid catalyst depends upon the __________ adsorption.
chemical
39
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 cannot be recovered chemically unchanged at the end of the chemical reaction.
A catalyst lowers the activation energy of the reacting molecules.
40
The dimensions of rate constant for reaction 3A --> B are (l/gm mole)/min. Therefore the reaction order is
2
41
Pick out the correct statement
A. Reactions with high activation energies are very temperature sensitive.
B. Chemical equilibrium is a static state.
C. A photochemical reaction is catalyzed by light.
D. A chemical reaction occurs when the energy of the react
Reactions with high activation energies are very temperature sensitive.
42
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
2
43
Sulphuric acid is used as a catalyst in the
alkylation of hydrocarbons.
44
Fractional conversion __________ with increase in pressure for ammonia synthesis reaction i.e., N2 + 3H2 <->2NH3.
increases
45
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 longitudinal direction.
C. Mixed reactor is always smaller than the plug flow reactor for all positive reaction orders for a particular duty.
46
The reason why a catalyst increases the rate of reaction is that, it
decreases the energy barrier for reaction.
47
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.
A. both conversion as well as concentration are same
B. conversion in both will be the same but concentrations will be different
C. both the conversion as well as concentrations will be different
D. none of these.
conversion in both will be the same but concentrations will be different
48
When the density of the reaction mixture is constant in a chemical reaction, the ratio of the mean residence time to space time is
1
49
In an ideal tubular-flow reactor
A. there is no mixing in longitudinal direction.
B. mixing takes place in radial direction.
C. there is a uniform velocity across the radius.
D. all (a), (b) and (c).
all (a), (b) and (c).
50
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?
2.5
51
__________ is the controlling step in a highly temperature sensitive fluid-solid non-catalytic reaction.
Chemical reaction
52
An autothermal reactor is
completely self-supporting in its thermal energy requirements.
53
The rate constant of a first order reaction depends on the
temperature.
54
A reaction in which one of the products of reaction acts as a catalyst is called a/an __________ reaction.
autocatalytic
55
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
1
56
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.
D. None of these.
Increasing the concentration of one or more of the products.
57
Conversion increases with increase in temperature in case of a an __________ reaction.
reversible endothermic
58
Effective diffusivity (DE) in a catalyst pellet is related to molecular diffusivity (DN) and Knudsen diffusivity (DK) as
1/DE = 1/DN + 1/DK
59
A photochemical reaction is __________ light.
initiated by
60
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 batch wise, while the other reactant is fed continuously.
C. In a continuous flow reactor, uniform concentration cannot 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.
In a continuous flow reactor, uniform concentration can not be maintained throughout the vessel even in a well agitated system
61
In a/an __________ reactor, there is exchange of heat with the surroundings with sizeable temperature variation.
non-adiabatic
62
Unreacted core model' represents the reaction involving
roasting of sulphide ores.
63
If a solid-gas non-catalytic reaction occurs at very high temperature, the rate controlling step is the __________ diffusion.
film
64
The units of frequency factor in Arhenious equation
are the same as those of the rate constant.
65
Which of the following is not a chemical step in a fluid solid catalytic reaction ?
A. Surface chemical reaction
B. Adsorption
C. Desorption
D. None of these
None of these
66
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:
K3 = K1.K2
67
In case of __________ reactions, the reaction rate does not decrease appreciably as the reaction proceeds.
auto catalytic
68
For nearly isothermal operation involving large reaction time in a liquid-phase reaction, the most suitable reactor is a __________ reactor.
stirred tank
69
B.E.T. method can be used to determine the __________ of a porous catalyst.
surface area
70
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
1
71
Which of the following is an independent variable for a batch tank reactor with uniform concentration and temperature?
A. Time
B. Useful volume of the tank
C. Diameter of the reactor
D. None of these
Time
72
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.
16
73
In a reversible chemical reaction having two reactants in equilibrium, if the concentration of the reactants are doubled, then the equilibrium constant will
remain the same
74
The equilibrium constant of a catalytic chemical reaction __________ due to the presence of a catalyst.
remains unaffected
75
The rate constant of a chemical reaction increases by increasing the
temperature
76
The catalytic activity of enzymes is due to their capacity to lower the __________ energy.
activation
77
Pick out the correct statement.
A. A lower temperature favors the reaction of lower activation energy.
B. The dispersion number for a reactor/vessel is uL/D.
C. The rate controlling step in a reaction involving many steps is the fastest step.
D. Pore volume and porosity of a catalyst is measured by BrunaverEmmet-Teller (BET) technique.
A lower temperature favours the reaction of lower activation energy.
78
The effect of increasing pressure on the gaseous equilibrium of the reaction 2X+3Y <-->3X+2Y indicates that
pressure has no effect.
79
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
(1 + x)
80
A batch reactor is characterised by
variation in extent of reaction and properties of the reaction mixture with time.
81
When a catalyst increases the rate of forward reaction, the value of rate constant
increases
82
Rate determining step in a reaction consisting of a number of steps in series is the __________ step.
slowest
83
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.
512
84
When all the limiting reactant is consumed in the reaction, the operational yield __________ the relative yield.
equals
85
The half life period of a first order reaction is
independent on initial concentration of the reactants.
86
The catalyst in a second order reversible reaction increases the rate of the forward reaction
and backward reaction equally.
87
Catalyst carriers
provide large surface area with a small amount of active material.
88
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.
0.6
89
In flow reactors, the performance equations interrelate the rate of reaction to the
A. feed rate.
B. reactor volume,
C. extent of reaction.
D. all (a), (b) and (c).
all (a), (b) and (c).
90
Space velocity
A. describes the extensive operating characteristics of a tubular flow reactor.
B. is the maximum feed rate pre unit volume of reactor for a given conversion.
C. is a measure of the ease of the reaction.
D. all (a), (b) and (c)
all (a), (b) and (c)
91
The rate of the chemical reaction A -->B doubles as the concentration of A i.e.., CA is doubled. If rate of reaction is proportional to CAn, then what is the value of n for this reaction ?
1
92
A reaction which is catalysed by a base is catalysed by all substances which have a tendency to
gain a proton
93
For a homogeneous reaction of nth order, the dimension of the rate constant is given by
(concentration)^1 - n/(time)
94
The fractional volume change between no conversion and complete conversion, for the isothermal gas phase reaction, 2A-->R, is
-0.5
95
The reaction in which one of the products of reaction acts as a catalyst is called a/an __________ reaction.
autocatalytic
96
A typical example of an exothermic reversible reaction conducted at high pressure in industry is
dehydration of ethanol.
97
Study of chemical kinetics is the easiest in the case of __________ reactions.
irreversible
98
In autocatalytic reactions,
one of the products acts as a catalyst.
99
Semibatch reactor is preferred, when a/an
A. a highly exothermic reaction is to be controlled.
B. undesirable side reaction (at high concentration of one of the reactants) is to be avoided.
C. a gas is to be reacted with liquid (e.g. hydrogenation of fat).
D. all (a), (b), and (c).
all (a), (b), and (c).
100
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
∞
101
What is the order of a chemical reaction whose rate is deter-mined by the variation of one concentration term only?
first
102
Pick out the wrong statement.
A. Visible radiation provides the necessary activation energy in photochemical reactions.
B. The order and molecularity of a complex reaction may not be the same.
C. For a second order reaction, the slope of the graph/plot between rate and (concentration) is equal to the rate constant (k).
D. Molecularity of the reaction is always a whole number greater than zero.
The order and molecularity of a complex reaction may not be the same.
103
The rate at which a chemical substance reacts is proportional to its
active mass
104
A plug-flow reactor is characterised by
presence of lateral mixing.
105
For a tubular reactor with space time 'τ' and residence time 'θ', the following statement holds good.
τ = θ , for an isothermic tubular reactor in which the density of the process fluid is constant.
106
Rate of an autocatalytic chemical reaction is a function of
Rate of an autocatalytic chemical reaction is a function of
A. temperature only.
B. pressure only.
C. composition only.
D. all (a), (b) and (c).
all (a), (b) and (c).
107
Which of the following curves shows the effect of temperature on the extent of gas-solid adsorption at a given pressure?
Adsorption isobar
108
For an ideal mixed flow reactor (CSTR), th
A. a dirac delta function
B. a step function.
C. a ramp function.
D. none of the above e exit age distribution E(t) is given by
none of the above
109
Fluid flow in a real packed bed can be approximated as __________ model.
dispersion
110
The 'E' curve for a non-ideal reactor defines the fraction of fluid having age between t and t + dt
at the outlet
111
To maximise the formation of R in the simultaneous reaction
A + B --> R , rR = 2CA^0.5.CB^2
A + B --> S , rS = 1.5 CA . CB
We should have
low CA, high CB
112
A reaction which is catalysed by an acid is also catalysed by any substance, which has a tendency to
lose a proton.
113
A stirred tank reactor compared to tubular-flow reactor provides
A. more uniform operating conditions.
B. permits operation at the optimum temperature for a long reaction time.
C. higher overall selectivity for a first order consecutive reaction.
D. all (a), (b) and (c)
all (a), (b) and (c)
114
A chemical reaction, A -->3B, is conducted in a constant pressure vessel. Starting with pure A, the volume of the reaction mixture increases 3 times in 6 minutes. The fractional conversion is
1
115
A catalyst inhibitor
A. lessens its selectivity.
B. may be useful for suppressing undesirable side reactions.
C. is added in small quantity during the catalyst manufacture itself.
D. all(a), (b) and (c).
all(a), (b) and (c).
116
In chamber process of sulphuric acid manufacture in industry, the gas phase oxidation of SO2 to SO3 is accomplished by a __________ reaction.
catalytic homogenous
117
If the rate of a chemical reaction becomes slower at a given temperature, then the
free energy of activation is higher.
118
The conversion XA and residence time data are collected for zero order liquid phase reaction in a stirred tank reactor. Which of the following will be a straight line ?
XA Vs . τ
119
The rate of the reaction, X--> Y, quadruples when the concentration of 'X' is doubled. The rate expression for the reaction is, r = K Cx^n, the value of 'n' in this case will be
2
120
The value of steric factor 'P' in the equation k = PZe^E/RT usually ranges from
1.0 to 10^-8
121
For a zero order reaction, the concentration of product increases with the
increase of reaction time.
122
Pick out the wrong statement.
A. 'Hold back' is defined as the fraction of material that stays longer than the mean residence time.
B. Study of non-ideal flow reactor is done experimentally by stimulus-response technique.
C. For studying a chemical reaction, it is desirable to monitor the reactants during initial stages and the products during the final stages of reaction.
D. A batch reactor cannot be used to study the kinetics of catalytic reaction.
A batch reactor can not be used to study the kinetics of catalytic reaction.
123
Effectiveness factor of a catalyst pellet is a measure of the __________ resistance.
pore diffusion
124
The rate expression for a heterogenous catalytic reaction is given by, - rA = K.KA PA(1 + KA.PA + KR.PR), where K is surface reaction rate constant and KA and KR are absorption equilibrium constants of A and R respectively. If KR PR >> (1 + KA PA), the apparent activation energy EA is equal to (given E is the activation energy for the reaction and ΔHR and ΔHA are the activation energies of adsorption of R and A)
E + ΔHA - ΔHR)
125
Given,
3H2 + CO = CH4 + H2O, KP = 101.84 and,
4H2 + CO2 = CH4 + 2H2O, KP = 101.17
the KP for the reaction CO + H2O = CO2 + H2 is
10^0.67
126
Differential method for analysing the kinetic data is used
for testing complicated mechanisms.
127
In case of the irreversible unimolecular type, first order reaction, the fractional conversion at any time for constant volume system as compared to variable volume system is
same
128
The reaction in which the rate equation corresponds to a stoichiometric equation, is called a/an __________ reaction.
elementary
129
A first order gaseous phase reaction is catalysed by a non-porous solid. The kinetic rate constant and the external mass transfer co-efficients are k and kg respectively. The effective rate constant (keff) is given by
1/keff = 1/k + 1/kg
130
Arrhenious equation represents graphically the variation between the __________ and temperature.
rate constant
131
__________ catalytic reaction is involved in the thermal cracking of gas oil.
Homogeneous
132
Variables affecting the rate of homogeneous reactions are
pressure, temperature and composition.
133
A chemical reaction occurs when the energy of the reacting molecules is __________ the activation energy of the reaction.
equal to or more than
134
Which of the following resistances is not involved in a gas phase catalytic (gas-solid) reaction?
A. Ash resistance.
B. Gas film and pore surface diffusion resistances for reactants.
C. Surface phenomenon resistance.
D. Gas film and pore surface diffusion resistances for products.
Ash resistance.
135
If the time required to change the concentration of reactant to half its original value is independent of the initial concentration, the order of reaction is
one
136
A batch adiabatic reactor at an initial temperature of 373°K is being used for the reaction, A-->B. Assume the heat of reaction is - 1kJ/mole at 373°K and heat capacity of both A and B to be constant and equal to 50J/mole.K. The temperature rise after a conversion of 0.5 will be
10°C
137
If CA is the quantity of reactants initially present, the quantity left after 'n' half periods will be equal to
(1/2)^n.CA
138
A photochemical reaction is
initiated by light.
139
The optimum performance for reactors operating in parallel is obtained when the feed stream is distributed in such a way, that the
space time for each parallel line is same.
140
A catalyst is said to be a negative catalyst, ifit
retards the rate of reaction.
141
For the non catalytic reaction of particles with surrounding fluid, the same needed to achive the same fractional conversion for particles of different unchanging sizes is proportional to the particle diameter, when the __________ is the controlling resistance.
chemical reaction
142
Pure ethanol vapor is fed to a reactor packed with alumina catalyst, at the rate of 100 kmole / hr. The reactor products comprise: ethylene :95 kmole / hr, water vapour: 97.5 k mole / hr and diethyl ether :2.5 kmole/hr. The reactions occuring can be represented by:
C2H5OH C2H4 + H2O
2C2H5OH C2H5 - O - C2H5 + H2O
The percent conversion of ethanol in the reactor is
100
143
Pick out the wrong statement.
A. The integral method of analyzing kinetic data is used when the data is scattered.
B. The differential method of analyzing kinetic data requires more accurate or larger amounts of data.
C. When the reaction rate is independent of temperature, the reaction is said to be of zero order.
D. The ratio of volumes of plug flow reactor to that of mixed reactor is always less than one for identical feed composition, flow rate, conversion and for all positive reaction orders.
When the reaction rate is independent of temperature, the reaction is said to be of zero order.
144
A backmix reactor
is same as ideal stirred tank reactor.
145
Rate of a chemical reaction is not influenced by the
number of molecules of reactants taking part in a reaction
146
Pick out the wrong statement:
A. Chemical reactions with high activation energy are very temperature sensitive.
B. A flat velocity profile exists in a plug flow reactor.
C. The residence time for all the elements of fluid in case of a P.F.R. need not be same.
D. Half life of a reaction increases with increased initial concentration for reaction orders more than one.
The residence time for all the elements of fluid in case of a P.F.R. need not be same.
147
The reaction A B is conducted in an adiabatic plug flow reactor (PFR). Pure A at a concentration of 2 kmol/m3 is fed to the reactor at the rate of 0.01 m3 /s and at a temperature of 500 K. If the exit conversion is 20%, then the exit temperature (in k)is (Data: Heat of reaction at 298 K = - 50000 kJ/ kmole of A reacted Heat capacities CPA = CPB = 100kJ/kmole. K (may be assumed to be independent of temperature))
600
148
Which of the following is not a theory of homogeneous reaction?
A. Collision theory and activated complex theory
B. Chain reaction theory
C. Radiation hypothesis
D. None of these
None of these
149
In a semi-batch reactor,
velocity of reaction can be controlled.
150
Which of the following is a controlling factor in very fast heterogeneous reaction?
A. Heat and mass transfer effects
B. Pressure
C. Temperature
D. Composition of reactant
Heat and mass transfer effects
151
Enzymes are destroyed, when the
temperature is very high,
152
For an autocatalytic reactor, the suitable reactor set up is
CSTR followed by P.F. reactor.
153
Ionic reactions occur in
solutions
154
The half life period of a first order reaction is given by (where, K = rate constant. )
0.693/K
155
Half life period of a chemical reaction is
the time required to reduce the concentration of the reacting substance to half its initial value.
156
In the gaseous phase ammonia formation reaction (N2 + 3H2<-->2NH3), the value of the equilibrium constant depends on the
temperature.
157
Transition state theory relates the above quantities as
k ∝ T.e^E/RT
158
Photochemical reaction rate does not depend significantly on temperature, because
the energy of reacting molecules exceeds the activation energy by absorption of light.
159
A CSTR is to be designed in which an exothermic liquid phase first order reaction of the type, A-->R, is taking place. The reactor is to be provided with a jacket in which coolant is flowing. Following data is given: CA0= 5 kmole/m3 ; XA = 0.5; Feed temperature = reactor temperature = 40°C. Rate constant at 40°C = 1 min-1 ; (ΔH) = - 40kJ/mole; ρ = 1000kg/m3 CP = 4 J/gm.°C ; q = 10-3 m3/min (ρ and CP are same for the reactant and product streams). The amount of heat to be removed is
5/3 kW
160
According to the 'law of mass action', the rate of reaction is directly proportional to the
molar concentration of the reactants.
161
For an ideal gas mixture undergoing a reversible gaseous phase chemical reaction, the equilibrium constant
increases with pressure.
162
In the reversible reaction of the type, A + B <--> AB, in general
the combination reaction will be exothermic, while the dissociation reaction will be endothermic.
163
A batch reactor is
suitable for liquid phase reactions involving small production rate.
164
For a first order reaction carried out in a plug flow reactor, the space time is
1/K ln Co/C
165
For an isothermal second order aqueous phase reaction, A --> B, the ratio of the time required for 90% conversion to the time required for 45% conversion is
11
166
A chemical reaction is of zero order, when the reaction rate is (where, CA = concentration of reactant)
A. ∝ CA.
B. ∝ 1/CA.
C. independent of temperature.
D. none of these.
none of these.
167
Pick out the wrong statement.
A. Catalytic activity of enzyme catalyzed reactions which is affected by temperature, pH value & chemical agents, is maximum at a temperature of about 45°C.
B. Most of the enzyme catalyzed reactions involve at least two substrates.
C. Enzymes help in increasing the activation energy of the reaction.
D. Equilibrium concentrations in enzyme catalyzed reactions can be calculated by using the thermodynamic properties of substrates & products.
Enzymes help in increasing the activation energy of the reaction.
168
There is no correspondence between stoichiometry and the rate equation in case of a/an __________ reaction.
non-elementary
169
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 7/8. Which of the following statement is true?
A. Inner catalyst core of radius R/8 does not participate in reaction.
B. Inner catalyst core of radius R/2 does not participate in reaction.
C. Inner catalyst core of radius 7R/8 does not participate in reaction.
D. Effectiveness factor for a zero order reaction cannot be 7/8 as it must always be 1.
Inner catalyst core of radius R/8 does not participate in reaction.
170
Which of the following is used for calcination of limestone and dolomite in industrial practice ?
A. Inner catalyst core of radius R/8 does not participate in reaction.
B. Inner catalyst core of radius R/2 does not participate in reaction.
C. Inner catalyst core of radius 7R/8 does not participate in reaction.
D. Effectiveness factor for a zero order reaction cannot be 7/8 as it must always be 1.
Moving bed reactor
171
An imbalanced chemical reaction equation is against the law of
conservation of mass
172
For the chemical reaction P-> Q, it is found that the rate of reaction doubles as the concentration of 'P' is doubled. If the reaction rate is proportional to Cp^n, then what is the value of 'n' for this chemical reaction ?
1
173
Which of the following is a characteristic of an ideal plug flow reactor ?
A. Axial dispersion
B. Flat velocity profile
C. Uniform mixing
D. None of these
Flat velocity profile
174
Velocity of a reaction depends upon the
A. nature of the reactants.
B. concentration of the reactants.
C. temperature at which the reaction is carried.
D. all (a), (b) and (c).
all (a), (b) and (c).
175
An isothermal aqueous phase reversible reaction, P <--> R, is to be carried out in a mixed flow reactor. The reaction rate in k.mole/m3 .h is given by, r = 0.5CP - 0.125CR. A stream containing only P enters the reactor. The residence time required (in hours) for 40% conversion of P is
1.6
176
What is the unit of the rate constant in a chemical reaction in which 10% of the reactant decomposes in one hour, 20% in two hours, 30% in three hours and so on ?
Litre/mole.second
177
For a fluidised bed reactor, the most suitable/relevant model is a __________ model.
bubbling bed
178
The rate at which a chemical substance reacts is proportional to its
active mass
179
In a reaction, the threshold energy is equal to (where, A = activation energy N = normal energy of reactants)
A+N
180
Thermodynamic equilibrium constant in a system is affected by
temperature
181
The most suitable reactor for carrying out an auto-thermal reaction is a
CSTR
182
Which of the following chemical reactions will be favoured by low pressure ?
N2O2 <--> 2NO2
183
A catalyst in a chemical reaction
A. decreases the activation energy
B. alters the reaction mechanism
C. increases the frequency of collisions of reacting species
D. all (a), (b) and (c)
all (a), (b) and (c).
184
Limiting reactant in a chemical reaction decides the
conversion
185
Consider the 'n' th order irreversible liquid phase reaction A --> B. Which one of the following plots involving half life of the reaction (t1/2) and the initial reactant concentration (CA0) gives a straight line plot ?
CA0 Vs ln t1/2
186
The rate of forward reaction, at chemical equilibrium is____the rate of backward reaction.
equal to
187
Pick the WRONG design guideline for a reactor in which the reactions, A -->R (desired) and A --> S (undesired) are to take place. The ratio of the reaction rates is https://www.indiabix.com/_files/images/chemical-engineering/chemical-reaction-engineering/478-493-1.png .
avoid recycle, when a > b.
188
With increase in temperature, the equilibrium __________ rises in case of endothermic reaction.
conversion
189
In case of a consecutive unimolecular type first order reaction, the concentration of component __________ increases continuously with time.
S
190
Enzymes (a protein) are catalysts found in organisms. Its efficiency of catalysing a reaction is due to its capacity to lower the activation energy of the reaction. The enzyme ptyalin used for food digestion is present in
saliva
191
Considering the endotheomic dissociation of CaCO3 in a closed vessel (CaCO3 <-->CaO + CO2), the pressure of CO2 increases, if
the temperature is increased.
192
The exit age distribution of fluid leaving a vessel is used to know the
extent of non-ideal flow in the vessel.
193
From Arhenius law, a plot of loge K versus 1/T gives a straight line with a slope of (-E/R). The unit of E/R is
°K
194
In the converter of the contact process for the manufacture of H2SO4 the equilibrium conversion of SO2 __________ (A) __________ with increase in temperature and __________ (B) __________ with increase in the mole ratio of SO2 to air.
(A) decreases (B) increases
195
For the irreversible elementary first order reaction in parallel viz., a plot of Cy Vs. Cz will give a straight line having a slope of
K1/K2
196
The time needed to achieve the same fractional conversion for particles of different sizes (d) when chemical reaction controls, is proportional to
d
197
A balanced chemical reaction equation conforms to the law of
conservation of mass
198
An exothermic reaction takes place in an adiabatic reactor. The product temperature __________ reactor feed temperature.
is always greater than
199
Reverse reaction in a chemical equilibrium is favoured by the
increase in the concentration of oneof the products.
200
Sum of the powers of the concentration terms in the rate equation is called the __________ of the reaction.
overall order
201
During manufacture of H2SO4, the oxidation of SO2 to SO3 by oxygen is an en-dothermic reaction. The yield of SO3 will be maximised, if the
temperature is reduced and pressure is increased.
202
The role of a catalyst in a chemical reaction is to change the
activation energy
203
The vessel dispersion number (D/μL) for plug flow is
0
204
BET apparatus is used to determine the
specific surface of a porous catalyst.
205
Carrier in a catalyst increases its
surface area
206
When the reaction occurs in the diffusion controlled region, the apparent activation energy as measured is only __________ the true value.
half
207
An isothermal irreversible reaction is being carried out in an ideal tubular flow reactor. The conversion in this case will __________ with decrease in space time.
decrease
208
Kinetics of a solid catalysed reaction can best be studied in a __________ reactor.
mixed
209
According to Arhenious equation of temperature dependency of rate constant for an elementary reaction
k ∝ e^-E/RT
210
The reactions of high molecularity are rare, because
of low probability of many body collisions.
211
Which of the following is the most suitable for isothermal operation ?
A. Batch reactor
B. Back-mix reactor
C. Plug-flow reactor
D. Fixed bed reactor
Back-mix reactor
212
For a first order chemical reaction, the rate constant
has unit of time-1.
213
Which of the following is an autocatalytic reaction ?
A. Photochemical reactions
B. Microbial fermentation reaction
C. Enzyme fermentation reaction
D. Ammonia synthesis reaction
Microbial fermentation reaction
214
The performance of a cascade of CSTR's can be improved by adding
more CSTR's in series.
215
A multiple reaction may be classified as a __________ reaction.
A. consecutive or side
B. parallel or side
C. mixed
D. all (a), (b) and (c)
all (a), (b) and (c)
216
Holding time for flow reactors is __________ the space time, for constant fluid density
equal to
217
Pick out the wrong statement.
A. In a multistep reaction, the slowest step is the rate determining step.
B. In general, the rate of a reaction becomes triple for every 10°C rise in temperature.
C. Slow chemical reactions have generally high values of activation energy.
D. Molecularity of a reaction can not be zero but the order of a reaction can be zero.
In general, the rate of a reaction becomes triple for every 10°C rise in temperature.
218
Arhenious equation shows the variation of __________ with temperature.
rate constant
219
When a catalyst increases the rate of chemical reaction, the rate constant
increases
220
In which of the following reactions, the equilibrium will shift to the right, if the total pressure is increased?
a. H2 + Cl2 <--> 2HCl
b. N2 + O2 <--> 2NO
c. N2O4 <--> 2 NO2
d. H2 + I2 <--> 2HI
N2 + O2 <--> 2NO
221
The catalyst in a first order chemical reaction changes the
activation energy
222
Oil is hydrogenated using nickel catalyst in a __________ reactor.
slurry
223
The performance equations for constant density systems are identical for
P.F.R. and batch reactor.
224
Reaction rate of a first order reaction, which is half completed in 23 minutes will be
0.03 min-1
225
Which of the following is the optimum operating condition for an exothermic reversible reaction taking place in a plug-flow reactor ?
a. Temperature should be high in the beginning and decreased towards the end of the reaction.
b. Very low temperature should be used throughout the reaction.
c. Very high temperature should be used throughout the reaction.
d. none of these.
Temperature should be high in the beginning and decreased towards the end of the reaction.
226
The half life period 't' of a zero order reaction, is equal to
CA0/2K
227
In case of calcination of limestone, CaCO3 CaO + CO2, the addition of more of CaO will result in __________ in the concentration of CO2.
no change
228
The rate of a homogeneous reaction is a function of
all temperature, pressure and composition.
229
In the fluid catalytic cracker (FCC), the cracking reaction is __________ (A) and the regeneration is___(B) __________
(A) endothermic (B) exothermic
230
Pick out the correct statement.
a. A catalyst does not change AH of the reaction.
b. A catalyst changes the equilibrium point.
c. Law of mass action was suggested by Le-Chatelier.
d. The difference between the energy of reactants and that of the products is the activation energy.
A catalyst does not change AH of the reaction.
231
Promoter is added to the catalyst to improve its
sensitivity
232
An irreversible first order reaction is being carried out in a CSTR and PFR of same volume. The liquid flow rates are same. The relative conversion will
be more in PFR than in CSTR.
233
When a high liquid hold up is required in a reactor for gas liquid reaction, use __________ coloumn.
bubble
234
In an exothermic reaction, the energy of the reacting substances as compared to that of products is
more
235
For a tubular flow reactor with uniform concentration and temperature, the independent variable is
length
236
Pick out the wrong statement.
a. For a first order consecutive reaction, a tubular flow reactor as compared to a stirred tank reactor provides higher overall selectivity.
b. 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.
c. Plug flow reactor (PFR) is always smaller than mixed reactor for all positive reaction orders for a particular duty.
d. Reaction rate does not decrease appreciably as the reaction proceeds in case of an autocatalytic reaction.
For a first order consecutive reaction, a tubular flow reactor as compared to a stirred tank reactor provides higher overall selectivity.
237
The extent of a reaction is
a. different for reactants and products.
b. dimensionless.
c. depends on the stoichiometric co-efficient.
d. all of the above.
all of the above.
238
Higher free energy of activation of a chemical reaction (at a given temperature) implies
slower rate of reaction.
239
Calcination reaction of limestone (CaCO3 --> CaO + CO2) goes to completion in the rotary kiln, because
CO2 escapes continuously.
240
The reactions with low activation energy are
fast
241
Molecularity of an elementary reaction, P + Q --> R + S is
4
242
Which of the following is not endothermic in nature ?
Combustion of sulphur.
243
The space time is equivalent to the holding time in a steady state mixed reactor for
constant fluid density systems.
244
The dispersion number of perfect mixed flow is
∞
245
An irreversible aqueous phase reaction, A + B --> P, is carried out in an adiabatic mixed flow reactor. A feed containing 4kmole/m3 of each A and B enters the reactor at 8m3 /hr. If the temperature of the exit stream is never to exceed 390 K, what is the maximum inlet feed temperature allowed?
Data: Heat of reaction = - 50 kJ/mole
Density of the reacting mixture = 1000kg/m3
Specific heat of reacting mixture = 2kJ/kg.K
The above data can be assumed to be independent of temperature and composition.
290
246
For a heterogenous catalytic reaction, A + B --> C, with equimole feed of A and B, the initial rate - rA0 is invariant with total pressure. The rate controlling step is
desorption of C.
247
Half life period of a first order irreversible reaction A B is
ln 2/k
248
Pick out the wrong statement.
a. Autocatalytic reactions are exemplified by microbial fermentation reactions.
b. The slowest step has the greatest influence on the overall reaction rate in case of an irreversible series reaction.
c. 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.
d. Hydrolysis of ester in presence of alkali or acid is a zero order reaction.
Hydrolysis of ester in presence of alkali or acid is a zero order reaction.
249
Which of the following is not a dimension-less group used in catalysis ? (where, D = dispersion co-efficient, cm2 /sec.D1 = diffusion co-efficient; cm2/sec L = length of the reactor, cm t = time, sec, v = volumetric flow rate, cm3/sec . V = volume, cm3.)
a. Reactor dispersion number (D/vL)
b. Reduced time
c. Thiele modulus
d. None of these
None of these
250
Pick out the wrong statement
a. For the same conversion, the holding time required in a batch reactor, is always equal to the space time required in a PFR.
b. Two mixed reactors of unequal size are available for producing a specified product, formed by a homogenous second order reaction. To achieve maximum production rate, the smaller reactor should be placed in series before the larger reactor.
c. Arrehenius equation describing the effect of temperature on rate constant is given by, K = A.e-Ea/RT
d.The mechanism for the decomposition of CH3CHO into CH4 and CO in presence of I2 is: CH3CHO +I2 CH3I + HI + CO; slow CH3I + HI CH4 + I2; fast Then the rate of disappearance of CH3CHO is equal to K.CCH3I.CHI and acts as a catalyst.
The mechanism for the decomposition of CH3CHO into CH4 and CO in presence of I2 is:
CH3CHO +I2 --> CH3I + HI + CO; slow
CH3I + HI --> CH4 + I2; fast
Then the rate of disappearance of CH3CHO is equal to K.CCH3I.CHI and acts as a catalyst.
251
The energy of activation of a chemical reaction
is the minimum energy which the molecules must have before the reaction can take place.
252
Chemical kinetics can predict the __________ of a chemical reaction.
rate
253
Which of the following fixes the volume of a batch reactor for a particular conversion and production rate?
a. Operating conditions (e.g. pressure and temperature)
b. Rate constant
c. Density of mixture
d. None of these
Density of mixture
254
Half life period of decomposition of a liquid 'A' by irreversible first order reaction is 12 minutes. The time required for 75% conversion of 'A' is __________ minutes.
24
255
With increase in the space time of an irreversible isothermal reaction being carried out in a P.F. reactor, the conversion will
increase
256
A catalyst promoter
improves the activity of a catalyst.
257
For the non-catalytic reaction of particles with surrounding fluid, the time needed to achieve the same fractional conversion for particles of different but unchanging sizes is proportional to the square of particle diameter, when the __________ is the controlling resistance.
diffusion through ash layer
258
If ΔG (free energy change) for a chemical reaction is very large and negative, then the reaction is
very much feasible.
259
In a zero order reaction, reactants concentration does not change with time and the
time for half change is half the time taken for completion of the reaction.
260
The minimum energy required to allow a chemical reaction to proceed is termed as the 'threshold energy '. Chemical reaction with low activation energy are
insensitive to temperature changes.
261
If Thiele modulus is __________ , then the pore diffusion resistance in a catalyst may be considered as negligible.
< 0.5
262
From collison theory, the reaction rate constant is proportional to
T^rn.exp(-E/RT)
263
For a mixed flow reactor operating at steady state, the rate of reaction is given by
FAo/V . XA
264
Catalytic action in a catalytic chemical reaction follows from the ability of catalyst to change the
activation energy
265
In Langmuir treatment of adsorption,
whole surface of the catalyst is essentially uniform and the adsorbed molecule has no effect on the rate of adsorption per site.
266
Organic catalysts differ from the inorganic catalyst in the sense that the former is
proteinous in nature.
267
An endothermic aqueous phase first order irreversible reaction is carried out in an adiabatic plug flow reactor. The rate of reaction
is maximum at the inlet of the reactor.
268
Pick out the wrong statement.
a. Exit age description function (E) and internal age distribution function (I) are related as, .
b. Chmisorption studies are useful in the determination of catalyst surface area and pore size distribution.
c. A higher temperature favours the reaction of higher activation energy.
d. A catalyst increases the potential energy barrier over which the reactants must pass to form products.
A catalyst increases the potential energy barrier over which the reactants must pass to form products.
269
An endothermic second order reaction is carried out in an adiabatic plug flow reactor. The rate of heat generation is
maximum at the inlet of the reactor.
270
Equilibrium of a chemical reaction as viewed by kinetics is a __________ state.
dynamic steady
271
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.
0.5
272
The size of plug flow reactor (PFR) for all positive reaction orders and for any given duty, is __________ that of mixed reactor.
smaller than
273
A space time of 3 hours for a flow reactor means that
the time required to process one reactor volume of feed (measured at specified conditions) is 3 hours.
274
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
3
275
The experimentally determined overall order of the reaction, A + B --> C + D, is two. Then the
reaction is elementary with a molecularity of 2.
276
In a continuous flow stirred tank reactor, the composition of the exit stream
is same as that in the reactor.
277
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.
no change
278
The energy balance equation over a tubular reactor under transient conditions is
a linear partial differential equation.
279
Which of the following factors control the deactivation of a porous catalyst pellet ?
a. Decay reactions.
b. Pore diffusion.
c. Form of surface attack by poison.
d. All (a), (b) and (c).
All (a), (b) and (c).
280
For the reaction, A + B -->2B + C,
rA = -rB
281
Transition state theory gives the rate constant as
K α T . e^-E/RT
282
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 ?
PFR followed by a CSTR followed by a PFR
283
Pick out the wrong statement.
a. Use of different catalysts in a reversible catalytic chemical reaction does not change the equilibrium composition.
b. Alumina is added as a promoter to iron catalyst in ammonia synthesis reaction.
c. Activation energy for a reaction is obtained from the intercept of the Ar-rhenious plot.
d. Presence of inerts affects the equilibrium conversion of reactants in a chemical reaction.
Activation energy for a reaction is obtained from the intercept of the Ar-rhenious plot.
284
In a reversible reaction, a catalyst increases the rate of forward reaction
and the backward reaction equally.
285
Maximum equilibrium conversion for endothermic reaction is obtained at the __________ temperature.
highest possible
286
When an exothermic reversible reaction is conducted adiabatically, the rate of reaction
continuously decreases.
287
For a first order chemical reaction in a porous catalyst, the Thiele modulus is 10. The effectiveness factor is approximately equal to
0.1
288
In solid catalysed reactions the diffusional effects are more likely to affect the overall rate of reaction for
fast reaction in catalyst of large pore diameter.
289
Helium-mercury method can be used to determine the __________ of the catalyst particle.
a. pore volume
b. solid density
c. porosity
d. all (a), (b), & (c).
all (a), (b), & (c).
290
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' ?
4
291
Chemical reaction rate of a component depends upon the
a. composition of the component only.
b. temperature of the system.
c. pressure of the system.
d. all (a), (b) and (c).
all (a), (b) and (c).
292
In a semi-batch reactor
velocity of reaction can be controlled.
293
A trickle bed reactor is the one, which
employs all the three phases (i.e.. .solid, liquid and gas).
294
The excess energy of the reactants required to dissociate into products is known as the __________ energy.
activation
295
In a/an __________ vessel, the fluid enters and leaves following plug flow.
closed
296
Shift conversion reaction
converts CO to CO2 with steam.
297
The importance of diffusion in a catalyst are increased by
a. large catalyst particle size.
b. an active surface of the catalyst.
c. small pore diameter.
d. all (a), (b) and (c).
all (a), (b) and (c).
298
A back mix reactor is
same as ideal stirred tank reactor.
299
Which one is the rate controlling step in a solid-gas non-catalytic reaction occurring at very high temperature?
Film diffusion
300
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
surface reaction between absorbed A and B in the gas phase.
301
What is the order of a chemical reaction in which doubling the initial concentration of the reactants doubles the half lifetime of the reaction?
0
302
The ratio of moles of a reactant converted into the desired product to that converted into unwanted product is called
selectivity
303
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
1/m
304
The eddy diffusivity for a liquid in plug flow must be
0
305
For the same residence time, which one will give the maximum conversion ?
Single tubular flow reactor (v = 5 litres).
306
__________ gas is normally employed in B.E.T.method of finding out the surface area of catalyst.
N2
307
The exit age distribution curve E(t) for an ideal CSTR with the average residence time, τ, is given by
[(e^-t/τ)/T]
308
The rate constant of a reaction depends on the
temperature of the system.
309
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 ?
0.338
310
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
PFR of volume V
311
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.
4
312
For a __________ order reaction, the units of rate constant and rate of reaction are the same.
zero
313
In case of staged packed bed reactors carrying out exothermic reaction, use
a. high recycle for pure gas.
b. plug flow for dilute liquid requiring no large preheating of feed.
c. cold shot operations for a dilute solution requiring large preheating to bring the stream upto the reaction temperature.
d. all (a), (b) and (c).
all (a), (b) and (c).
314
Vegetable oils are hydrogenated in a __________ reactor.
slurry
315
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
1/3
316
The rate of reaction does not decrease appreciably as the reaction proceeds in case of __________ reactions.
autocatalytic
317
For all positive reaction orders for a particular duty,
mixed reactor is always larger than the plug-flow reactor.
318
The heat of reaction
is independent of the mechanism of reaction.
319
Which of the following does not produce a change in the value of rate constant of a reaction ?
Concentration and catalyst
320
With increase in temperature, the equilibrium conversion of a reversible exothermic reaction
decreases
321
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.) ?
2/3
322
As the chemical reaction proceeds, the rate of reaction
decreases.
323
Pick out the wrong statement.
a. A catalyst does not alter the final position of equilibrium in a reversible reaction.
b. A catalyst initiates a reaction.
c. A catalyst is specific in reaction.
d. A catalyst remains unchanged in chemical composition at the end the reaction.
A catalyst initiates a reaction.
324
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.
same as
325
Photo-chemical reactions occur in presence of
sunlight.
326
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
V
327
Knudsen diffusion is directly proportional to
sqrt of T
328
Fractional conversion __________ for an exothermic reversible chemical reaction, when the temperature is maximum.
decreases
329
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
2τ
330
On application of pressure to the equilibrium system, ice <--> water ; which of the following phenomenon will occur ?
a. Water will evaporate
b. Equilibrium will not be attained
c. More ice will be formed
d. More water will be formed.
More water will be formed.
331
Participation of __________ is involved in the occurrence of a chemical reaction.
electrons
332
Promoter.
a. initiates a chemical reaction and is a catalyst by itself.
b. atlers the position of equilibrium in a reversible reaction.
c. increases the number of active centres by increasing the unevenness of catalyst surface and by creating discontinuities in the crystals.
d. all (a), (b) and (c).
increases the number of active centres by increasing the unevenness of catalyst surface and by creating discontinuities in the crystals.
333
The rate constant of a reaction is a function of the
temperature of the system.
334
Mean residence time is equal to the space time, when
a. the feed rate is measured at temperature and pressure in the reactor.
b. the temperature, pressure and the density of reaction mixture remains constant throughout the reactor.
c. there is no change in number of moles in gaseous reaction.
d. all (a), (b) and (c).
all (a), (b) and (c).
335
If 'n' is the order of reaction, then unit of rate constant is
1/(time)(concentration)^(n - 1)
336
Batch process is preferred over continuous process, when the
a. product yields and quality can not be achieved in continuous process, because of long residence time.
b. sales demand of product is not steady.
c. same equipment can not be used for several processes of the same nature.
d. all (a), (b) & (c)
all (a), (b) & (c)
337
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.
3
338
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
higher in P.F. reactor
339
For any reaction, we may write conversion as a function of
a. time
b. temperature
c. concentration
d. all (a), (b) & (c)
all (a), (b) & (c)
340
The use of space time is preferred over the mean residence time in the design of a/an
ideal tubular-flow reactor
341
Autocatalytic reactions are best carried out in a
recycle reactor
342
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
5/8
343
A batch reactor suffers from following disadvantage.
a. Poor product quality control.
b. High labour and handling cost.
c. High shutdown time requirement for emptying, cleaning and refilling.
d. All (a), (b)and(c).
All (a), (b)and(c).
344
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
equal in size.
345
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.
3
346
Half life period of a chemical reaction is proportional to CA0-1 , if the reaction is of __________ order.
second
347
The irreversible reaction, X --> Y, is the special case of the reversible reaction, X <-->Y, in which the
a. equilibrium constant is infinite.
b. fractional conversion of 'A' at equilibrium is unity.
c. concentration of 'A' at equilibrium is zero.
d. all (a), (b) and (c).
all (a), (b) and (c).
348
The equilibrium constant K of a chemical reaction depends on
temperature only.
349
The reaction rate almost gets doubled for 10°C rise in temperature. This is due to the fact that the
fraction of molecules having threshold energy increases.
350
Which of the following is not a unit of reaction rate ?
a. Moles for med/(surface of catalyst) (time)
b. Moles formed/volume of reactor) (time)
c. Mole formed/volume of catalyst) (time)
d. None of these
None of these
351
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 ?
a. Langmuir's assumption applies to every adsorbed layer.
b. There is no dynamic equilibrium between successive layer.
c. The adsorbed layer may be polymolecular in thickness and the heat of adsorption in each layer (except the first one) is involved in each of the evaporation process.
d. none of these.
There is no dynamic equilibrium between successive layer.
352
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
15, 10, 5
353
The unit of frequency factor in Arhenious equation is
same as that of rate constant.
354
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)
increases
355
Reaction of benzene with chlorine gas to produce tri-chlorobenzene exemplifies a/an __________ reaction.
consecutive
356
For the gaseous reaction 2A --> B, where the feed consists of 50 mole % A and 50 mole % inerts, the expansion factor is
-0.25
357
The molecularity and the order of reaction respectively, for the hydrolysis of methyl acetate in presence of acids are
2 & 1
358
The irreversible reaction is a special case of reversible reaction, if the
reactant concentration at equilibrium condition is zero.
359
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 kmole/m3 , the volume of the mixed flow reactor should be increased by a factor of
7
360
For the liquid phase parallel reactions:
R, rR = K1.CA2; E1 = 80 KJ/mole
S, rs= K1.CA ; E2 = 120 KJ/mole
The desired product is R. A higher selectivity of R will be achieved, if the reaction is conducted at
high temperature in a PFR.
361
In an ideal mixed reactor (at steady state), the
a. space time is equivalent to holding time for constant density systems.
b. composition throughout the reactor remains same.
c. exit stream has the same composition as the fluid within the reactor.
d. all (a), (b) and (c).
all (a), (b) and (c).
362
The knowledge of initial concentration and rate constant is necessary to determine the half life time of a reaction of __________ order.
second
363
Which of the following factors control the design of a fluid-solid reactor ?
a. Reaction kinetics for single particle,
b. Size distribution of solids beingtreated.
c. Flow patterns of solids and fluid in the reactor.
d. All (a), (b) and (c).
All (a), (b) and (c).
364
A Catalyst
shortens the time to reach the equilibrium.
365
The synthesis of proteins and metabolism in biological objects occur in the presence of biocatalyst called
fungi
366
Pick out the wrong statement.
a. A particular chemical reaction is more temperature sensitive at low temperatures.
b. A very high value of equilibrium constant, K (K >> 1) indicates that the reaction is practically irreversible in nature.
c. The intercept of the Arrhenious plot is called the 'activation energy'.
d. Non-ideal flow takes place in reactors due to recycling, channeling or by creation of stagnant regions.
The intercept of the Arrhenious plot is called the 'activation energy'.
367
Kinetics of a catalytic reaction can be best studied on a/an __________ reactor.
a. mixed
b. integral (plug flow)
c. differential (flow)
d. either (a), (b) and (c).
either (a), (b) and (c).
368
In case of a __________ reactor, the composition in the reactor and at the exit of the reactor is the same.
back-mix
369
Exothermic reactions are best carried out in
CSTR followed by a plug flow reactor.
370
Reactions with high activation energy are
very temperature sensitive
371
In case of a/an __________ chemical reaction, conversion increases with the rise in temperature.
reversible endothermic
372
A space velocity of 5 hr-1 means that
five reactor volumes of feed (at specified conditions) are being fed into the reactor per hour.
373
With increase in initial concentration, the fractional conversion of a first order reaction in a given time
remains constant
374
The rate of reaction of a/an __________ reaction is not affected by temperature rise.
photochemical
375
With an increase in pressure in gaseous phase chemical reactions, the fractional conversion __________ when the number of moles decreases.
increases
376
Half-life period for a first order reaction is __________ the initial concentration of the reactant.
independent of
377
Carbon particles accummulated on the catalyst used in the gas oil cracking lies in the category of __________ poison.
deposited
378
The decomposition of A into B is represented by the exothermic reaction, A <--> 2B. To achieve maximum decomposition, it is desirable to carry out the reaction.
at low P and low T.
379
The catalytic converter for conversion of SO2 to SO3 by contact process should have a feed with SO2 content between
7-10%
380
If the pore diffusion controls in a catalytic reaction, the apparent activation energy Ea is equal to
ED/2
381
What is the dispersion number for a plug flow reactor ?
0
382
Collision theory gives the rate constant for bimolecular reaction as
K α e^-E/RT
383
Find a mechanism that is consistent with the rate equation and reaction given below:
2A + B --> A2B, ( - rA) = k.CA.CB
A + A <--> AA;AA + B --> A2B
384
A gaseous reactant is introduced in a mixed reactor of 3 litres volume at the rate of 1 litre/second. The space time is __________ seconds.
3
385
The temperature dependence of reaction rate constant (K) by Arhenius law is given by
K α e^-E/RT
386
Velocity of a chemical reaction
a. decreases with increase in temperature.
b. increases with increase of pressure of reactants for all reactions.
c. decreases with increase of reactant concentration.
d. none of these.
none of these.
387
Backmixing is most predominant in
a single CSTR.
388
If helium is introduced in a reactor containing O2, SO2 and SO3 at equilibrium, so that total pressure increases while volume and temperature remains constant. In this case the dissociation of SO3 (as per Le Chatlier principle)
decreases
389
Fluidised bed reactor is characterised by
uniformity of temperature.
390
Space time equals the mean residence time
when the density of the reaction mixture is constant.
391
A liquid decomposes by irreversible first order kinetics and the half life period of this reaction is 8 minutes. The time required for 75% conversion of the liquid will be __________ minutes.
16
392
Rate constant 'k' and absolute temperature 'T' are related by collision theory (for bimolecular) as
k ∝ sqrt(T)
393
The conversion for a first order liquid phase reaction. A --> B in a CSTR is 50%. If another CSTR of the same volume is connected in series, then the % conversion at the exit of the second reactor will be
75
394
What is the dispersion number for a CSTR?
∞
395
Rate of a chemical reaction is independent of the concentration of the reactants for a __________ reaction.
zero order
396
With increase in temperature, the rate constant obeying Arhenious equation
increases.
397
Bulk diffusion in catalyst pore __________ with increase in pressure.
increases
398
Pick out the correct statement.
a. A chemical reaction accompanied by absorption of heat is called an exothermic reaction.
b. A chemical reaction accompanied by evolution of heat is called an endothermic reaction.
c. The rate constant for a first order reaction does not change on changing the concentration units.
d. Chemical equilibrium state is dynamic in nature.
The rate constant for a first order reaction does not change on changing the concentration units.
399
The concentration of A in a first order reaction, A --> B, decreases
exponentially with time.
400
The equilibrium constant of chemical reaction __________ in the presence of catalyst.
remains unaffected
401
The order of a chemical reaction is
an experimentally determined quantity.
402
A chemical reaction occurs, when the energy of the reacting molecules is __________ the activation energy of reaction.
equal to or more than
403
In the hydrodealkylation of toluene to benzene, the following reactions occur:
C7H8 + H2 --> C6H6 + CH4
2C6H6 <--> C12H10 + H2
Toluene and hydrogen are fed to a reactor in a molar ratio 1:5.80% of the toluene gets converted and the selectivity of benzene(defined as moles of benzene formed/moles of toluene converted) is 90%. The fractional conversion of hydrogen is
0.144
404
Catalyst is a substance, which __________ chemical reaction.
can either increase or decrease the speed of a
405
The residence time distribution of an ideal CSTR is
exp (-t/τ)
406
A rise in temperature
a. normally tends to increase the reaction rate.
b. does not affect a catalysed reaction.
c. does not affect photo-chemical reaction rates.
d. all (a), (b) and (c).
all (a), (b) and (c).
407
The enzyme which can catalyse the conversion of glucose to ethyl alcohol is
zymase
408
For reaction, P + 2 -->3R, molar rate of consumption of P is
half of that of Q.
409
If pore diffusion is the controlling step in a solid catalysed reaction, the catalyst
porosity is of less importance.
410
The conversion of a reactant, undergoing a first order reaction, at a time equal to three times the half life of the reaction is
0.875
411
In which of the following gaseous phase reversible reactions, the product yield can not be increased by the application of high pressure ?
a. N2 + O2 <--> 2NO
b. PCl3 + Cl2 <--> PCl5
c. N + 3H2 <--> 2NH3
d. 2SO2 + O2 <--> 2SO3
N2 + O2 <--> 2NO
412
What is the value of 'n' if the reaction rate of the chemical reaction A --> B, is proportional to CAn and it is found that the reaction rate triples, when the concentration of 'A' is increased 9 times ?
1/2
413
A second order reaction of the form A + B --> C is called a pseudo-first order reaction, when
CB0 ≥ CB0
414
Pick out the wrong statement.
In a first order reaction, A products; the reaction becomes slower as it proceeds, because the concentration of A decreases and the rate is proportional to the concentration of A.
a. Transition state theory approaches the problem of calculating reaction rates by concentrating on the idea of activated complexes.
b. According to the penetration theory, the mass transfer co-efficient decreases, if the exposure time of an eddy to the solute decreases.
c. If the rate of an irreversible reaction, A + B 2C is k.CA.CB, then the reaction is always elementary.
d. If the rate of an irreversible reaction, A + B 2C is k.CA.CB, then the reaction is always elementary.
According to the penetration theory, the mass transfer co-efficient decreases, if the exposure time of an eddy to the solute decreases.
415
Inversion of cane sugar is an example of
bimolecular reaction with first order.
416
Pick out the correct statement.
a. A catalyst speeds up the forward reaction but slows shown the reverse reaction.
b. Addition of catalyst changes the equilibrium constant.
c. Pressure changes do not change the equilibrium concentrations.
d. The composition of equilibrium is changed by catalyst.
Pressure changes do not change the equilibrium concentrations.
417
In which of the following gaseous phase reactions, the equilibrium of the reaction remains unaffacted by pressure changes ?
a. 2O3 <--> 3O2
b. N2 + O2 <--> 2NO
c. 2NO2 <--> N2O4
d. 2SO2 + O2 <--> 2SO3
N2 + O2 <--> 2NO
418
The rate of a gas phase reaction is given by K . CA . CB. If the volume of the reaction vessel is reduced to l/4th of its initial volume, then the reaction rate compared to the original rate will be __________ times.
16
419
Rate of a chemical reaction is not affected by the
number of molecules of reactants taking part in the reaction.
420
Overall rate of reaction in a heterogenous catalytic reaction depends upon the mass and energy transfer from the fluid to solid surface and its rate of reaction is usually __________ the concentration of catalyst, if it does not entail a chain mechanism.
proportional to
421
__________ resistance is not involved in the combustion of a carbon particle.
Ash
422
In an ideal P.F.R. at steady state conditions
the conversion of the reactant varies from point to point along a flow path.
423
B.E.T. method of finding out surface area of a catalyst, uses the extension of __________ isotherm.
Langmuir
424
An example of autothermal reactor operation is
ethylene oxidation
425
For a packed bed reactor; the presence of a long tail in the residence time distribution curve is an indication of
dead zone
426
For a first order isothermal chemical reaction in a porous catalyst, the effectiveness factor is 0.3. The effectiveness factor will increase if the
catalyst size is reduced or the catalyst diffusivity is increased.
427
Cold shot cooling is only practical when the feed temperature is __________ than the reaction temperature.
much lower
428
The preferred reacting system for oxidation of o-xylene to phthalic anhydride is
jacketted liquid phase CSTR.
429
The effectiveness factor for large value of Thiele modulus (L.sqrt(K/D1)) of a solid catalysed first order reaction is equal to (where, L = length of the reactor, cm, D1 = diffusion co-efficient, cm2/second)
1/(LK/D1))
430
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 at the external surface, the process is limited by
diffusion within the pellet.
