bce Flashcards
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.
semi fluidized
_________ explains the mechanism of catalysis.
A. Activated complex theory
B. Collision theory
C. Thermodynamics
D. None of these
activated complex
he fractional volume change of the system for the isothermal gas phase
reaction, A → 3B, between no conversion and complete conversion is
A. 0.5
B. 1
C. 2
D. 3
2
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.
lowers the activation energy of reacting molecules.
What is the order of a chemical reaction,
A 2B C + ⎯k→
, 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
B. 7/4
C. 5/2
D. 5/4
7/2
For high conversion in a highly exothermic solid catalyzed reaction, use a
__________ bed reactor.
A. fixed
B. fluidized bed reactor followed by a fixed
C. fixed bed reactor followed by a fluidized
D. fluidized
luidized bed reactor followed by a fixed
. 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. 8
B. 12
C. 16
D. 32
16
A first order reaction requires two equal sized CSTR. The conversion is
A. less when they are connected in series.
B. more when they are connected in series.
C. more when they are connected in parallel.
D. same whether they are connected in series or in parallel
more when they are connected in series.
In case of physical adsorption, the heat of adsorption is of the order of
__________ kcal/kg-mole.
A. 100
B. 1000
C. 10000
D. 100000
100000
The most unsuitable reactor for carrying out reactions in which high reactant
concentration favors high yields is
A. backmix reactor
B. plug flow reactor
C. series of CSTR
D. PFR in series
backmix reactor
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
he space velocity of 3 hr-1 means that one third reactor volume
of feed at specified conditions are being fed
A reactor is generally termed as an autoclave, when it is a
A. high pressure batch reactor.
B. atmospheric pressure tank reactor.
C. high pressure tubular reactor.
D. atmospheric pressure CSTR
high pressure batch reactor.
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. 100%
B. 95%
C. 75%
D. 20%
95%
The rate constant of a chemical reaction decreases by decreasing the
A. pressure
B. concentration of reactants
C. temperature
D. duration of reaction
temperature
action rate equation for the reaction,
R + 2S → X + Y
is
2
R S
R K C C
dt
dC
− = . If S at is present in large excess, what is the order
of this reaction?
A. zero
B. one
C. two
D. three
one
Rate of a gaseous phase reaction is given by,
2
A
A K p
dt
dp
− = . The
unit of rate constant is
A. (atm)-1
B. (hr)-1
C. (atm)-1.(hr)-1
D. atm.(hr)-1
(atm)-1.(hr)-1
__________ is the response curve for a step input signal from a reactor.
A. S-curve
B. C-curve
C. I-curve
D. none of these
c-curve
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. pressure
B. temperature
C. both (a) & (b)
D. neither (a) nor (b)
temperature
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
tubular
The reaction between oxygen and organic material is a/an __________
reaction.
A. exothermic
B. endothermic
C. biochemical
D. photochemical
exothermic
With decrease in temperature, the equilibrium conversion of a reversible
endothermic reaction
A. decreases
B. increases
C. remains unaffected
D. increases linearly with temperature
decreases
In an exothermic chemical reaction, the reactants compared to the products
have
A. higher temperature
B. more energy
C. less energy
D. same energy
more energy
For a reaction of the type,
V 1 X 2 Y 3 Z ⎯⎯K → ⎯⎯K → ⎯⎯K →
, the rate of reaction (- rx) is
given by
A. (K1+K1)CX
B. (K1+K2+K3)CX
C. K1CV - K2CX
D. (K1-K2)CX
K1CV - K2CX
In a consecutive reaction system
A 1 B
2 C ⎯⎯E → ⎯⎯E →
when E1
is much greater than E2, the yield of B increases with the
A. increase of temperature.
B. decrease of temperature.
C. increase in initial concentration of A.
D. decrease in initial concentration of A.
increase of temperature.
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
A. decreases.
B. increases.
C. is at the highest allowable temperature throughout.
D. first increases and then decreases.
is at the highest allowable temperature throughout.
. The rate constant of a chemical reaction increases by 100 times when the
temperature is increased from 400 °K to 500 °K. Assuming transition state
theory is valid, the value of E/R is
A. 8987°K
B. 9210°K
C. 8764°K
D. 8621°K
8764°K
A batch reactor is suitable for
A. achieving cent percent conversion of reactants into products.
B. large scale gaseous phase reactions.
C. liquid phase reactions.
D. obtaining uniform polymerization products in highly exothermic
reactions
liquid phase reactions
For a heterogeneous catalytic reaction
A. free energy of activation is lowered in the presence of catalyst,
which remains unchanged at the end of reaction.
B. a relatively small amount of catalyst can cause the conversion of
large amount of reactants which does not mean that catalyst
concentration is important.
C. the catalyst does not form an intermediate complex with the reactant.
D. the surface of the catalyst does not play an important role during
reaction.
free energy of activation is lowered in the presence of catalyst,
which remains unchanged at the end of reaction.
The increase in the rate of reaction with temperature is due to
A. increase in the number of effective collisions.
B. decrease in activation energy.
C. increase in the average kinetic energy of the reacting molecules.
D. none of these.
decrease in activation energy
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
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.
A. first
B. second
C. third
D. Any
any
For the irreversible elementary reactions in parallel viz
X 2 Y ; X 1 Z ⎯⎯k → ⎯⎯k →
, the rate of disappearance of ‘X’ is
equal to
A. CA(K1+K2)
B. CA(K1 + K2)/2
C. CA . K1/2
D. CA . K2/2
CA(K1+K2)
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 c
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
Radioactive decay follows __________ order kinetics.
A. first
B. second
C. third
D. zero.
first
The excess energy of reactants in a chemical reaction required to dissociate
into products is termed as the __________ energy.
A. activation
B. potential
C. binding
D. threshold
activation
For a solid catalyzed chemical reaction, the effectiveness of solid catalyst
depends upon the __________ adsorption.
A. physical
B. chemical
chemical
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.
The dimensions of rate constant for reaction 3A → B are (l/gm mole)/min.
Therefore the reaction order is
A. 0
B. 1
C. 2
D. 3
2
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 reacting
molecule is less than the activation energy of the reaction.
Reactions with high activation energies are very temperature
sensitive.
. 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
A. 0
B. 1
C. 2
D. 3
2
Sulphuric acid is used as a catalyst in the
A. hydrogenation of oils.
B. gas phase oxidation of SO2 in chamber process.
C. alkylation of hydrocarbons.
D. none of these.
alkylation of hydrocarbons
Fractional conversion __________ with increase in pressure for ammonia
synthesis reaction i.e., N2 + 3H2 2NH3.
A. increases
B. decreases
C. remains unchanged
D. unpredictable from the data
increases
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.
Mixed reactor is always smaller than the plug flow reactor for
all positive reaction orders for a particular duty.
The reason why a catalyst increases the rate of reaction is that, it
A. decreases the energy barrier for reaction.
B. increases the activation energy.
C. decreases the molecular collision diameter.
D. none of these
decreases the energy barrier for reaction
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
When the density of the reaction mixture is constant in a chemical reaction,
the ratio of the mean residence time to space time is
A. > 1
B. < 1
C. 1
D. 0
1
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
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 Arrhenius law is used. What
will be this ratio, if transition state theory is used with the same value of E/R?
A. 1.6
B. 2
C. 2.24
D. 2.5
2.5
_________ is the controlling step in a highly temperature sensitive fluidsolid non-catalytic reaction.
A. Gas film diffusion
B. Ash diffusion
C. Chemical reaction
D. none of these
chemical reaction
An autothermal reactor is
A. most suitable for a second order reaction.
B. most suitable for a reversible reaction.
C. completely self-supporting in its thermal energy requirements.
D. isothermal in nature.
completely self-supporting
The rate constant of a first order reaction depends on the
A. concentration of the reactant.
B. temperature.
C. concentration of the product.
D. time.
temperature
A reaction in which one of the products of reaction acts as a catalyst is called
a/an __________ reaction.
A. catalytic
B. autocatalytic
C. photochemical
D. none of these
autocatalytic
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
A. ∞
B. 0
C. 1
D. > 1
1
Which of the following will favor 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.
Conversion increases with increase in temperature in case of a an
__________ reaction.
A. autocatalytic
B. irreversible
C. reversible endothermic
reversible endothermic
Effective diffusivity (DE) in a catalyst pellet is related to molecular
diffusivity (DN) and Knudsen diffusivity (DK) as
A. DE = DM + DK
B. sum of reciprocals
C. DE = DM DE
D. DE = DN/DE
sum of reciprocals
A photochemical reaction is __________ light.
A. initiated by
B. accompanied with emission of
C. catalyzed by
D. used to convert heat energy into
initiated by
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 cannot be
maintained throughout the vessel even in a well agitated system.
In a/an __________ reactor, there is exchange of heat with the surroundings
with sizeable temperature variation.
A. adiabatic
B. isothermal
C. non-adiabatic
D. none of these
non-adiabatic
‘Unreacted core model’ represents the reaction involving
A. combustion of coal particles.
B. roasting of sulphide ores.
C. manufacture of carbon disulphide from elements.
D. none of these.
roating of sulphide ores
. If a solid-gas non-catalytic reaction occurs at very high temperature, the rate
controlling step is the __________ diffusion.
A. film
B. ash layer
C. pore
D. none of these
film
The units of frequency factor in Arrhenius equation
A. are the same as those of the rate constant.
B. depend on the order of the reaction.
C. depend on temperature, pressure etc. of the reaction.
D. are cycles per unit time.
are the same as those of the rate constant.
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
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) + 2H2 O(g) CO2(g) + 4H2(g)
Then K1, K2 and K3 are related as:
K3=K1K2
In case of __________ reactions, the reaction rate does not decrease
appreciably as the reaction proceeds.
A. catalytic
B. parallel
C. series
D. auto catalytic
AUTOCATALYTICS\
For nearly isothermal operation involving large reaction time in a liquidphase reaction, the most suitable reactor is a __________ reactor.
A. stirred tank
B. tubular flow
C. batch
D. fixed bed
stirred tank
What is the Thiele modulus of the solid catalyzed first order reaction,
X Y ⎯k→
, if the pore diffusion offers negligible resistance to reaction ?
A. < 5
B. < 0.5
C. > 1
D. 5
<0.5
B.E.T. method can be used to determine the __________ of a porous
catalyst.
A. solid density
B. pore volume
C. surface area
D. all (a), (b) and (c)
surface area
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/liter to 50 gm moles/liter is same
as that required to reduce it from 2 gm moles/liter to 1 gm mole/liter in the same
volume. Then the order of this reaction is
A. 0
B. 1
C. 2
D. 3
1
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
For reactions in parallel viz A → P (desired product) and A → Q (unwanted
product), if the order of the desired reaction is higher than that of the undesired
reaction, a
A. batch reactor is preferred over a single CSTR for high yield.
B. tubular reactor is preferred over a single CSTR for high yield.
C. both (a) and (b).
D. single CSTR is the most suitable.
both a a nd b
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.
A. 8
B. 16
C. 1/8
D. 1/16
16
In a reversible chemical reaction having two reactants in equilibrium, if the
concentration of the reactants is doubled, then the equilibrium constant will
A. remain the same
B. be halved
C. also be doubled
D. become one fourth
remain the same
The equilibrium constant of a catalytic chemical reaction __________ due
to the presence of a catalyst.
A. increases
B. decreases
C. remains unaffected
D. unpredictable from the data
remains unaffected
The rate constant of a chemical reaction increases by increasing the
A. temperature
B. pressure
C. reactant’s concentration
D. none of thes
temperature
The catalytic activity of enzymes is due to their capacity to lower the
__________ energy.
A. activation
B. potential
C. kinetic
D. none of these
activation
A first order reaction requires two unequal sized CSTR. Which of the
following gives higher yield?
A. Large reactor followed by smaller one.
B. Smaller reactor followed by larger one.
C. Either of the arrangement (a) or (b) will give the same yield.
D. Data insufficient can’t be predicted.
either
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 favors the reaction of lower activation
energy
The effect of increasing pressure on the gaseous equilibrium of the reaction
2X + 3Y 3X + 2Y indicates that
A. pressure has no effect.
B. backward reaction is favored.
C. forward reaction is favored.
D. none of these.
pressure has no effect
A batch reactor is characterized by
A. constant residence time.
B. variation in extent of reaction and properties of the reaction
mixture with time.
C. variation in reactor volume.
D. very low conversion.
variation in extent of reaction and properties of the reaction
. 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
A. (1 + x)
B. (1 - x)
C. (1 + x)2
D. (1 - x)2
1+x
When a catalyst increases the rate of forward reaction, the value of rate
constant
A. increases
B. decreases
C. remain same
D. becomes infinite
increases
Rate determining step in a reaction consisting of a number of steps in series
is the __________ step.
A. fastest
B. slowest
C. intermediate
D. data insufficient; can’t be predicted
slowest
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
from 10 to 100°C.
A. 256
B. 512
C. 112
D. 612
512
When all the limiting reactant is consumed in the reaction, the operational
yield __________ the relative yield.
A. is greater than
B. is smaller than
C. equals
D. can be either greater or smaller than (depends on the type of
reaction)
equals
The half life period of a first order reaction is
A. always the same irrespective of the reaction.
B. dependent on initial concentration of the reactants.
C. proportional to the initial concentration of reactants.
D. half the specific rate constant.
dependent on initial concentration of the reactants.
The catalyst in a second order reversible reaction increases the rate of the
forward reaction
A. and decreases that of backward reaction.
B. and backward reaction equally.
C. only.
D. to a greater extent than that of the backward reaction.
and backward reaction equally
Catalyst carriers
A. have very high selectivity.
B. increase the activity of a catalyst.
C. provide large surface area with a small amount of active
material.
D. inhibit catalyst poisoning.
provide large surface area with a small amount of active
material.
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.
A. 0.15
B. 0.30
C. 0.60
D. 0.90
0.60
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 c
