Chemical Reactions Engineering Part 2 Flashcards
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
0.8
1.33
1.6
2.67
1.6
-rA=0.5Cp - 0.125Cr.
-rA=0.5Cpo(1-Xa) - 0.125(Cro-CroXa),
-rA = 0.5 Cpo(1-Xa) - 0.125Cpo(M+Xa),
For MFR:
(t/Cpo) = Xa/-rA,
t = 0.4/((0.5(1-0.4))-0.125(0+0.4)),
t = 1.6.
Design of heterogeous catalytic reactor involves consideration of __________ steps.
only chemical
only physical
both (a) & (b)
neither (a) nor (b)
both (a) & (b)
A consecutive reaction, A –C1–> B –C2–> C , is characterised by
maxima in the concentration of A.
maxima in the concentration of B.
maxima in the concentration of C.
high exothermicity.
maxima in the concentration of B.
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
Moles/litre.second
Litre/mole
Litre/second
Litre/mole.second
For a fluidised bed reactor, the most suitable/relevant model is a __________ model.
tank in series
bubbling bed
plug flow
none of these
bubbling bed
The rate at which a chemical substance reacts is proportional to its
active mass
molecular weight
equivalent weight
atomic weight
active mass
In a reaction, the threshold energy is equal to (where, A = activation energy N = normal energy of reactants)
A
N
A+N
A-N
A+N
Thermodynamic equilibrium constant in a system is affected by
inerts
pressure
temperature
all (a), (b) & (c)
temperature
The most suitable reactor for carrying out an auto-thermal reaction is a
batch reactor
CSTR
semi-batch reactor
plug-flow reactor
CSTR
Which of the following chemical reactions will be favoured by low pressure ?
2HI <–> H2 + I2
N2O2 <–> 2NO2
N2 + O2 <–> 2NO
none of these
N2O2 <–> 2NO2
A catalyst in a chemical reaction
decreases the activation energy.
alters the reaction mechanism.
increases the frequency of collisions of reacting species.
all (a), (b) and (c).
all (a), (b) and (c).
Slurry reactors are characterised by the
lack of intraparticle diffusion resistance.
presence of two mobile phases.
both (a) and (b).
neither (a) nor (b).
both (a) and (b).
Limiting reactant in a chemical reaction decides the
rate constant
conversion
reaction speed
equilibrium constant
conversion
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 t1/2
ln CA0 Vs t1/2
CA0 Vs ln t1/2
ln CA0 Vs ln t1/2
CA0 Vs ln t1/2
The rate of forward reaction, at chemical equilibrium is____the rate of backward reaction.
more than
less than
equal to
either (b) or (c)
equal to
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 rR/rS = (k1/k2)CA^(a-b) .
use high pressure and eliminate inerts, when a > b.
avoid recycle, when a > b.
use batch reactor or plug flow reactor, when a > b.
use CSTR with a high conversion, when a > b.
avoid recycle, when a > b.
With increase in temperature, the equilibrium __________ rises in case of endothermic reaction.
constant
conversion
both (a) & (b)
neither (a) nor (b)
conversion
In case of a consecutive unimolecular type first order reaction A –K1–> R –K2–> S , the concentration of component __________ increases continuously with time.
S
R
A
none of these
S
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
blood
saliva
intestine
gland
saliva
saliva ptyalin
Considering the endotheomic dissociation of CaCO3 in a closed vessel (CaCO3 <–>CaO + CO2), the pressure of CO2 increases, if
a catalyst is added.
the temperature is increased.
an inert gas is pumped keeping the temperature constant.
none of these.
the temperature is increased.
The exit age distribution of fluid leaving a vessel is used to know the
activation energies of a reaction.
reaction mechanism.
extent of non-ideal flow in the vessel.
none of these.
extent of non-ideal flow in the vessel.
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 cal
k cal/ K
K
k cal. K
K
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) increases (B) decreases
(A) decreases (B) increases
(A) increases (B) increases
(A) decreases (B) decreases
(A) decreases (B) increases
For the irreversible elementary first order reaction in parallel viz. X –k1–> Y; X –k2–> Y , a plot of Cy Vs. Cz will give a straight line having a slope of
K2/K1
K1/K2
K1 . K2
K1 + K2
K1/K2
The time needed to achieve the same fractional conversion for particles of different sizes (d) when chemical reaction controls, is proportional to
d
sqrt(2)
d^1.5
d^2
d
A balanced chemical reaction equation conforms to the law of
conservation of mass
Avagadro’s hypothesis
gaseous volumes
none of these
conservation of mass
An exothermic reaction takes place in an adiabatic reactor. The product temperature __________ reactor feed temperature.
is always equal to
is always greater than
is always less than
may be greater or less than
is always greater than
Reverse reaction in a chemical equilibrium is favoured by the
removal of one of the products regularly.
increase in the concentration of oneof the products.
increase in the concentration of one of the reactants.
none of these.
increase in the concentration of oneof the products.
The equilibrium constant for the reversible reaction, A <–K1,K2–> P , is affected by the
temperature of the system.
presence or absence of inerts.
pressure of the system.
kinetics of the reaction.
pressure of the system.
Sum of the powers of the concentration terms in the rate equation is called the __________ of the reaction.
order
overall order
molecularity
none of these
overall order
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 increased.
pressure is reduced.
temperature is increased and pressure is reduced.
temperature is reduced and pressure is increased.
temperature is reduced and pressure is increased.
The role of a catalyst in a chemical reaction is to change the
equilibrium constant
activation energy
final products
heat of reaction
activation energy
The vessel dispersion number (D/uL) for plug flow is
0
500
750
infinite
0
Molecularity of a reaction
is always equal to the overall order of reaction.
may not be equal to the order of reaction.
can’t have a fractional value.
both (b) and (c).
both (b) and (c).
BET apparatus is used to determine the
specific surface of a porous catalyst.
pore size distribution.
pore diameter.
porosity of the catalyst bed.
specific surface of a porous catalyst.
BETSS - BET Specific Surface
Carrier in a catalyst increases its
surface area
activity
performance
none of these
surface area
When the reaction is dominated by in-traparticle diffusion, the apparent order of reaction (nD) as measured is related to the true order (n) as
nD = (n+1)/2
nD = n/2
nD = n + 1
none of these
nD = (n+1)/2
When the reaction occurs in the diffusion controlled region, the apparent activation energy as measured is only __________ the true value.
twice
half
equal
none of these
half
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.
increase
increase exponentially
decrease
remain unchanged
decrease
An elementary liquid phase decomposition reaction A –k–> 2B is to be carried out in a CSTR. The design equation is
kT = XA/(1 - XA)
kT = XA(1 + XA)/(1 + XA)
kT = XA/(1 - XA)^2
kTCAo = [XA/(1 - XA)^2]/(1-XA)^2
kT = XA/(1 - XA)
Kinetics of a solid catalysed reaction can best be studied in a __________ reactor.
batch
plug-flow
mixed
none of these
mixed
According to Arhenious equation of temperature dependency of rate constant for an elementary reaction
k is proportional to sqrt(T)
k is proportional to e^-E/RT
k is proportional to T e^-E/RT
none of these
k is proportional to e^-E/RT
The reactions of high molecularity are rare, because
of very large activation energy of many bodies.
of low probability of many body collisions.
many body collisions are not favoured energetically.
of requirement of very large concentration for such reactions.
of low probability of many body collisions.
Which of the following is the most suitable for isothermal operation ?
Batch reactor
Back-mix reactor
Plug-flow reactor
Fixed bed reactor
Back-mix reactor
For a first order chemical reaction, the rate constant
changes on changing the concentration units.
is not a function of the unit of time.
has unit of time-1.
none of these.
has unit of time-1.
Which of the following is an autocatalytic reaction ?
Photochemical reactions
Microbial fermentation reaction
Enzyme fermentation reaction
Ammonia synthesis reaction
Microbial fermentation reaction
The performance of a cascade of CSTR’s can be improved by adding
a P.F. reactor in series.
a P.F. reactor in parallel.
more CSTR’s in series.
more CSTR’s in parallel.
more CSTR’s in series.
A multiple reaction may be classified as a __________ reaction.
consecutive or side
parallel or side
mixed
all (a), (b) and (c)
all (a), (b) and (c)
Holding time for flow reactors is __________ the space time, for constant fluid density
double
triple
equal to
none of these.
equal to
Pick out the wrong statement.
In a multistep reaction, the slowest step is the rate determining step.
In general, the rate of a reaction becomes triple for every 10 C rise in temperature.
Slow chemical reactions have generally high values of activation energy.
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.
The order of the reaction, H2 + Cl2 —Sunlight—> 2HCl , is
0
1
2
3
0
Arhenious equation shows the variation of __________ with temperature.
reaction rate
rate constant
energy of activation
frequency factor
rate constant
When a catalyst increases the rate of chemical reaction, the rate constant
decreases
increases
remains constant
becomes infinite
increases
In which of the following reactions, the equilibrium will shift to the right, if the total pressure is increased?
H2 + Cl2 <–> 2HCl
N2 + O2 <–> 2NO
N2O4 <–> 2 NO2
H2 + I2 <–> 2HI
N2 + O2 <–> 2NO
The catalyst in a first order chemical reaction changes the
equilibrium constant
activation energy
heat of formation of the product
heat of reaction
activation energy
Oil is hydrogenated using nickel catalyst in a __________ reactor.
batch
slurry
fluidised bed
fixed bed
slurry
oil/veg oil slurry
The performance equations for constant density systems are identical for
P.F.R. and backmix reactor.
P.F.R. and batch reactor.
P.F.R, batch reactor and backmix reactor.
batch reactor and backmix reactor.
P.F.R. and batch reactor.
Reaction rate of a first order reaction, which is half completed in 23 minutes will be
0.03 sec-1
0.03 min-1
0.03 hr-1
0.05 min-1
0.03 min-1
Which of the following is the optimum operating condition for an exothermic reversible reaction taking place in a plug-flow reactor ?
Temperature should be high in the beginning and decreased towards the end of the reaction.
Very low temperature should be used throughout the reaction.
Very high temperature should be used throughout the reaction.
none of these.
Temperature should be high in the beginning and decreased towards the end of the reaction.
The half life period ‘t’ of a zero order reaction, A –K–> Products , is equal to
CA0/2K
CA0/K
0.693/K
1/K
CA0/2K
The point selectivity of the product ‘Y’ in the reaction, X –K1–> Y; X –K2–> Z is equal to
K1/K2
K2/K1
K1-K2
K2-K1
K1/K2
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
increase
decrease
unpredictable from the data
no change
The rate of a homogeneous reaction is a function of
temperature and pressure only.
temperature and composition only.
pressure and composition only.
all temperature, pressure and composition.
all temperature, pressure and composition.
In the fluid catalytic cracker (FCC), the cracking reaction is __________ (A) and the regeneration is___(B) __________
(A) exothermic (B) endothermic
(A) exothermic (B) exothermic
(A) endothermic (B) enodthermic
(A) endothermic (B) exothermic
(A) endothermic (B) exothermic
cracking-endo regeneration-exo
Pick out the correct statement.
A catalyst does not change AH of the reaction.
A catalyst changes the equilibrium point.
Law of mass action was suggested by Le-Chatelier.
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.
Promoter is added to the catalyst to improve its
porosity
sensitivity
surface area
none of these
sensitivity
PISS promoter improve sensitivty
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 CSTR than in PFR.
be more in PFR than in CSTR.
be same in both cases.
depend on the temperature.
be more in PFR than in CSTR.
When a high liquid hold up is required in a reactor for gas liquid reaction, use __________ coloumn.
packed
spray
tray
bubble
bubble
In an exothermic reaction, the energy of the reacting substances as compared to that of products is
more
less
same
either (a) or (b), depends on order of reaction.
more
For a tubular flow reactor with uniform concentration and temperature, the independent variable is
time
length
diameter
none of these
length
Pick out the wrong statement.
For a first order consecutive reaction, a tubular flow reactor as compared to a stirred tank reactor provides higher overall selectivity.
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.
Plug flow reactor (PFR) is always smaller than mixed reactor for all positive reaction orders for a particular duty.
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.
wrong tubular compared to stirred tank provides higher overall…
The extent of a reaction is
different for reactants and products.
dimensionless.
depends on the stoichiometric co-efficient.
all of the above.
all of the above.
Higher free energy of activation of a chemical reaction (at a given temperature) implies
slower rate of reaction.
higher rate of reaction.
higher equilibrium conversion.
both (b) and (c).
slower rate of reaction.
Calcination reaction of limestone (CaCO3 –> CaO + CO2) goes to completion in the rotary kiln, because
CaO is not dissociated.
CO2 escapes continuously.
of high calcination temperature.
CaO is more stable than CaCO3.
CO2 escapes continuously.
The reactions with low activation energy are
always spontaneous
slow
fast
non-spontaneous
fast
Molecularity of an elementary reaction, P + Q –> R + S is
1
2
3
4
4
Which of the following is not endothermic in nature ?
Combustion of sulphur.
Gasification of carbon.
Thermal cracking of fuel oil.
Steam reforming of naphtha.
Combustion of sulphur.
not endo. sulphur comb.
The rate of an autocatalytic reaction, A + B –k–> B + B , is given by -rA = k . CA . CB. In this case, the
plot of - rA Vs CA is a straight line with slope k.
plot of - rA Vs CA is a hyperbola.
rate of disappearance of reactant A is maximum, where CA = CB
both ‘b’ & ‘c’
both ‘b’ & ‘c’
The space time is equivalent to the holding time in a steady state mixed reactor for
non-isothermal gas reaction.
variable fluid density systems.
constant fluid density systems.
gas reactions with changing no. of moles.
constant fluid density systems.
The dispersion number of perfect mixed flow is
0
> 150
infinite
< 2100
infinite
For the reaction 2X + Y –K–> Z , the rate of formation of Z is 0.2 gm mole/litre.hr. what is the rate of disappearance of X in gm mole/litre. hr ?
0.4
0.1
0.2
none ofthese
0.4
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.
190
290
390
490
290
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
surface Kc/(1 + TS) reaction between absorbed A and B in the gas phase.
surface reaction between absorbed A and absorbed B.
surface reaction between A in the gas phase and absorbed B.
desorption of C.
desorption of C.
Half life period of a first order irreversible reaction A B is
k/2
ln k/2
ln 2/k
ln 0.5/k
ln 2/k
Pick out the wrong statement.
Autocatalytic reactions are exemplified by microbial fermentation reactions.
The slowest step has the greatest influence on the overall reaction rate in case of an irreversible series reaction.
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.
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.
wrong - hydrolysis of ester
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.)
Reactor dispersion number (D/vL)
Reduced time (vt/V)
Thiele modulus [L sqrt(k/D1)]
None of these
None of these
Pick out the wrong statement
For the same conversion, the holding time required in a batch reactor, is always equal to the space time required in a PFR.
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.
Arrehenius equation describing the effect of temperature on rate constant is given by, K = A.e^-Ea/RT
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.
The energy of activation of a chemical reaction
is same as heat of reaction at constant pressure.
is the minimum energy which the molecules must have before the reaction can take place.
varies as fifth power of the temperature.
both (b) and (c).
is the minimum energy which the molecules must have before the reaction can take place.
Chemical kinetics can predict the __________ of a chemical reaction.
rate
feasibility
both (a) & (b)
neither (a) nor (b)
rate
Which of the following fixes the volume of a batch reactor for a particular conversion and production rate?
Operating conditions (e.g. pressure and temperature)
Rate constant
Density of mixture
None of these
Density of mixture
Volume change for unimolecular type first order reaction A –K–> 4R , increases __________ with time.
linearly
exponentially
parabolically
logarithmically
exponentially
volume change A4R exponentially
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.
18
24
6
12
24
Decomposition rate of a liquid ‘X’ which decomposes as per the reaction X –K1–> A, X –K2–> B, X –K3–> C is given by
K1 . CX
(K1 + K2 + K3)CX
(K1 + K2)CX
(K2 + K3)CX
(K1 + K2)CX
With increase in the space time of an irreversible isothermal reaction being carried out in a P.F. reactor, the conversion will
increase
decrease
remain same
data in insufficient; can’t be predicted
increase
A catalyst promoter
improves the activity of a catalyst.
acts as a catalyst support.
itself has very high activity.
all (a), (b) and (c).
improves the activity of a catalyst.
In case of a P.F.R., there
may be lateral mixing of fluid.
should not be any mixing along the flow path.
both (a) and (b).
neither (a) nor (b).
both (a) and (b).
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.
film diffusion
diffusion through ash layer
chemical reaction
either (a), (b) or (c)
diffusion through ash layer
If delta-G (free energy change) for a chemical reaction is very large and negative, then the reaction is
not feasible.
just feasible.
very much feasible.
unpredictable as delta-G is no measure of feasibility of a reaction.
very much feasible.
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.
time for half change is independent of the initial concentration.
time for completion of the reaction is independent of the initial concentration.
reaction rate is trebled when the initial concentration is trebled.
time for half change is half the time taken for completion of the reaction.
The minimum energy required to allow a chemical reaction to proceed is termed as the ‘threshold energy ‘. Chemical reaction with low activation energy are
always irreversible.
insensitive to temperature changes.
mostly irreversible.
highly temperature sensitive.
insensitive to temperature changes.
low activation - insensitive to temp changes
If Thiele modulus is __________ , then the pore diffusion resistance in a catalyst may be considered as negligible.
0
infinite
< 0.5
> 0.5
< 0.5
From collison theory, the reaction rate constant is proportional to
exp (-E/RT)
exp (-E/2RT)
sqrt(T)
T^rn.exp(-E/RT)
T^rn.exp(-E/RT)
For a mixed flow reactor operating at steady state, the rate of reaction is given by
FAo/V - dCA/dt
FAo/V + dCA/dt
FAo/V . XA
-dCA/dt
FAo/V . XA
Catalytic action in a catalytic chemical reaction follows from the ability of catalyst to change the
activation energy
equilibrium constant
heat of reaction
none of these
activation energy
In Langmuir treatment of adsorption,
whole surface of the catalyst does not have the same activity for adsorption and there is attraction between the adsorbed molecule.
whole surface of the catalyst is essentially uniform and the adsorbed molecule has no effect on the rate of adsorption per site.
all the adsorption does not take place by the same mechanism.
extent of adsorption is more than one complete monomolecular layer on the surface.
whole surface of the catalyst is essentially uniform and the adsorbed molecule has no effect on the rate of adsorption per site.
Langmuir - whole surface uniform
Organic catalysts differ from the inorganic catalyst in the sense that the former is
active at cryogenic temperatures only.
prohibitively costly.
proteinous in nature.
active at very high temperature only.
proteinous in nature.
inorganic catalyst proteinous
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.
goes through a maximum along the length of the reactor.
goes through a minimum along the length of the reactor.
is maximum at the exit of the reactor.
is maximum at the inlet of the reactor.
Pick out the wrong statement.
Exit age description function (E) and internal age distribution function (I) are related as, E = -dI/do.
Chmisorption studies are useful in the determination of catalyst surface area and pore size distribution.
A higher temperature favours the reaction of higher activation energy.
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.
For an ideal plug flow reactor, the value of Peclet number is
0
infinite
1
10
0
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.
maximum at the exit of the reactor.
maximum at the centre of the reactor.
constant throughout the reactor.
maximum at the inlet of the reactor.
Equilibrium of a chemical reaction as viewed by kinetics is a __________ state.
dynamic steady
static steady
dynamic unsteady
none of these
dynamic steady
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
1
2
3
0.5
The size of plug flow reactor (PFR) for all positive reaction orders and for any given duty, is __________ that of mixed reactor.
greater than
equal to
smaller than
unpredictable from the data
smaller than
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.
three reactor volumes of feed can be processed every hour.
it takes three hours to dump the entire volume of the reactor with feed.
conversion is cent per cent after three hours.
the time required to process one reactor volume of feed (measured at specified conditions) is 3 hours.
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
1
2
3
0
3
The experimentally determined overall order of the reaction, A + B –> C + D, is two. Then the
reaction is elementary with a molecularity of 2.
molecularity of the reaction is 2, but the reaction may not be elementary.
reaction may be elementary with molecularity of 2.
reaction is elementary but the molecularity may not be 2.
reaction is elementary with a molecularity of 2.
In a continuous flow stirred tank reactor, the composition of the exit stream
is same as that in the reactor.
is different than that in the reactor.
depends upon the flow rate of inlet stream.
none of these.
is same as that in the reactor.
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.
decrease
increase
no change
either (a) or (b), depends on the type of reaction
no change
The energy balance equation over a tubular reactor under transient conditions is
an ordinary non-linear differential equation.
an algebric differential equation.
a linear partial differential equation.
a non-linear partial differential equation.
a linear partial differential equation.
Which of the following factors control the deactivation of a porous catalyst pellet ?
Decay reactions.
Pore diffusion.
Form of surface attack by poison.
All (a), (b) and (c).
All (a), (b) and (c).
For the reaction, A + B –>2B + C,
rA = rB
rA = -rB
rA = 2rB
rA = rB/2
rA = -rB
Transition state theory gives the rate constant as
K α e^-E/RT
K α e^E/RT
K α T . e^-E/RT
K α √T. e^-E/RT
K α T . e^-E/RT
arrhenius → K α e^-E/RT
transition state → K α T . e^-E/RT
collision → K α √T. e^-E/RT
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 ?
CSTR followed by a PFR
PFR followed by a CSTR
CSTR followed by a PFR followed by a CSTR.
PFR followed by a CSTR followed by a PFR.
PFR followed by a CSTR followed by a PFR.
Pick out the wrong statement.
Use of different catalysts in a reversible catalytic chemical reaction does not change the equilibrium composition.
Alumina is added as a promoter to iron catalyst in ammonia synthesis reaction.
Activation energy for a reaction is obtained from the intercept of the Ar-rhenious plot.
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.
In a reversible reaction, a catalyst increases the rate of forward reaction
only.
to a greater extent than that of the backward reaction.
and decreases that of the backward reaction.
and the backward reaction equally.
and the backward reaction equally.
Maximum equilibrium conversion for endothermic reaction is obtained at the __________ temperature.
highest possible
lowest possible
intermediate
room
highest possible
When an exothermic reversible reaction is conducted adiabatically, the rate of reaction
continuously increases.
continuously decreases.
passes through a maximum.
passes through a minimum.
passes through a maximum.
exothermic reversible adiabatic rate passes maximum
For a first order chemical reaction in a porous catalyst, the Thiele modulus is 10. The effectiveness factor is approximately equal to
1
0.5
0.1
0
0.1
The rate equation for the reaction represented by X –K–> Y , is given by - rx = K1 . Cx/(1 + K2 Cx). At high value of Cx (i.e.., K2Cx > > 1), the order of the reaction and the rate constant are respectively
zero order & K1/K2
zero order & K1
first order & K1
first order & K1/K2
zero order & K1/K2
In solid catalysed reactions the diffusional effects are more likely to affect the overall rate of reaction for
fast reactions in catalyst of small pore diameter.
fast reaction in catalyst of large pore diameter.
slow reactions in catalyst of small pore diameter.
slow reactions in catalyst of large pore diameter.
slow reactions in catalyst of small pore diameter.
diffusional effects - slow small
Helium-mercury method can be used to determine the __________ of the catalyst particle.
pore volume
solid density
porosity
all (a), (b), & (c).
all (a), (b), & (c).
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
1/4
16
2
4
Chemical reaction rate of a component depends upon the
composition of the component only.
temperature of the system.
pressure of the system.
all (a), (b) and (c).
all (a), (b) and (c).
In a semi-batch reactor
velocity of reaction can be controlled.
maximum conversion can be controlled.
both the reactants flow counter-currently.
residence time is constant.
velocity of reaction can be controlled.
A trickle bed reactor is the one, which
has altogether three streams either entering or leaving.
processes three reactants at different flow rates.
processes three reactants with same flow rate.
employs all the three phases (i.e.. .solid, liquid and gas).
employs all the three phases (i.e.. .solid, liquid and gas).
What is the order of a chemical reaction in which doubling the initial concentration of the reactants doubles the half life time of the reaction ?
0
1
2
3
0
The excess energy of the reactants required to dissociate into products is known as the __________ energy.
thermal
activation
threshold
binding
activation
excess activation energy
In a/an __________ vessel, the fluid enters and leaves following plug flow.
open
closed
open-closed
close-opened
closed
Shift conversion reaction
converts N2 and H2 into NH3.
converts CO to CO2 with steam.
is non-catalytic.
is highly exothermic.
converts CO to CO2 with steam.
shift CO CO2
The importance of diffusion in a catalyst are increased by
large catalyst particle size.
an active surface of the catalyst.
small pore diameter.
all (a), (b) and (c).
all (a), (b) and (c).
A back mix reactor is
suitable for gas phase reactions.
ideal at very low conversion.
same as plug flow reactor (PFR).
same as ideal stirred tank reactor.
same as ideal stirred tank reactor.
backmix-idealstirred
Which one is the rate controlling step in a solid-gas non-catalytic reaction occurring at very high temperature?
Pore diffusion
Film diffusion
Ash layer diffusion
Chemical reaction
Film diffusion
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
absorption of A.
surface reaction between absorbed A and absorbed B.
surface reaction between absorbed A and B in the gas phase.
surface reaction between A in the gas phase and absorbed B.
surface reaction between absorbed A and B in the gas phase.
For a __________ order chemical reaction, A –K–> products , the half life period is independent of the initial concentration of the reactant A.
zero
first
second
third
first
The ratio of moles of a reactant converted into the desired product to that converted into unwanted product is called
operational yield
relative yield
selectivity
none of these
selectivity
selectivity desired/unwanted
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
m
1/m
√m
m²
1/m
The eddy diffusivity for a liquid in plug flow must be
1
0
infinite
between 0 and 1
0
eddy plug flow 0
For multiple reactions, the flow pattern within the vessel affects the
size requirement
distribution of reaction products
both (a) and (b)
neither (a) nor (b)
both (a) and (b)
The rate expression for the gaseous phase reaction, CO + 2H2 –> CH3OH, is given by, r = k1 PCO . PH2 - k2 . PCH3OH, α = PCO, β = PH2, γ = PCH3OH . Which of the following is not possible ?
α = 1, β = 1, γ =1
α = 1, β = 2, γ = 1
α = 1/3, β = 2/3, γ = 1/3
α = 1/2, β = 1, γ = 1/2
α = 1, β = 1, γ =1
