Chemical Reactions Engineering Part 3 Flashcards
For the same residence time, which one will give the maximum conversion ?
Single stirred tank (v = 5 litres).
Two stirred tank (each of 2.5 litres) in series.
Stirred tank followed by tubular flow reactor (each of 2.5 litres).
Single tubular flow reactor (v = 5 litres).
Single tubular flow reactor (v = 5 litres).
__________ gas is normally employed in B.E.T.method of finding out the surface area of catalyst.
N2
H2
CO2
He
N2
The exit age distribution curve E(t) for an ideal CSTR with the average residence time, T, is given by
e^-t/T
[(e^-t/T)/T]
1 - e^-t/T
1-[(e^-t/T)/T]
[(e^-t/T)/T]
etTT
The rate constant of a reaction depends on the
initial concentration of reactants.
time of reaction.
temperature of the system.
extent of reaction.
temperature of the system.
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 ?
0.253
0.338
0.152
0.637
0.338
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
CSTR of volume V
PFR of volume V
CSTR of volume V/X
PFR of volume V/X
PFR of volume V
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.
3
4
6
8
4
For a __________ order reaction, the units of rate constant and rate of reaction are the same.
zero
first
second
fractional
zero
In case of staged packed bed reactors carrying out exothermic reaction, use
high recycle for pure gas.
plug flow for dilute liquid requiring no large preheating of feed.
cold shot operations for a dilute solution requiring large preheating to bring the stream upto the reaction temperature.
all (a), (b) and (c).
all (a), (b) and (c).
Vegetable oils are hydrogenated in a __________ reactor.
slurry
plug flow
homogeneous catalytic
none of these
slurry
veg oil slurry
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
1/2
1/3
1/4
1/5
1/3
gas 50% A3B 1/3 mole fraction
The rate of reaction does not decrease appreciably as the reaction proceeds in case of __________ reactions.
autocatalytic
exothermic
endothermic
autothermal
autocatalytic
For all positive reaction orders for a particular duty,
mixed reactor is always larger than the plug-flow reactor.
ratio of the volume of the mixed reactor to that of the plug-flow reactor decreases with order.
reactor size is independent of the type of flow.
density variation during reaction affects design.
mixed reactor is always larger than the plug-flow reactor.
The heat of reaction
depends on the pressure only.
depends on the mechanism of reaction only.
depends on both pressure and mechanism of reaction.
is independent of the mechanism of reaction.
is independent of the mechanism of reaction.
Which of the following does not produce a change in the value of rate constant of a reaction ?
Pressure
Temperature
Concentration and catalyst
None of these.
Concentration and catalyst
With increase in temperature, the equilibrium conversion of a reversible exothermic reaction
decreases
increases
remains unaffected
decreases linearily with temperature
decreases
In a CSTR __________ varies with time.
reaction rate
concentration
both (a) & (b)
neither (a) nor (b)
neither (a) nor (b)
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.) ?
1/3
1/2
2/3
2
2/3
As the chemical reaction proceeds, the rate of reaction
increases.
decreases.
remains same.
may increase or decrease depending on the type of reaction.
decreases.
Pick out the wrong statement.
A catalyst does not alter the final position of equilibrium in a reversible reaction.
A catalyst initiates a reaction.
A catalyst is specific in reaction.
A catalyst remains unchanged in chemical composition at the end the reaction.
A catalyst initiates a reaction.
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.
more than
less than
same as
data insufficient; can’t be predicted.
same as
1 0.5 10 5 same as
Photo-chemical reactions occur in presence of
sunlight.
darkness.
solid catalysts.
monochromatic radiation only.
sunlight.
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/n
V
V.n
1/V
V
Knudsen diffusion is directly proportional to
T
sqrt(T)
1/sqrt(T)
T^2
sqrt(T)
Fractional conversion __________ for an exothermic reversible chemical reaction, when the temperature is maximum.
increases
remains unchanged
decreases
unpredictable from the data
decreases
Non-catalytic fluid-solid reactions are represented by __________ model.
continuous reaction
unreacted core
both (a) and (b)
neither (a) and (b)
both (a) and (b)
A pulse tracer is introduced in an ideal CSTR (with a mean residence time ?) at time, t = 0. The time taken for the exit concentration of the tracer to reach half of its initial value will be
2T
0.5T
T/0.693
0.693T
2T
pulse tracer 2T
On application of pressure to the equilibrium system, ice <–> water ; which of the following phenomenon will occur ?
Water will evaporate
Equilibrium will not be attained
More ice will be formed
More water will be formed.
More water will be formed.
pressure ice water more water
Participation of __________ is involved in the occurrence of a chemical reaction.
protons
neutrons
electrons
none of these
electrons
Promoter.
initiates a chemical reaction and is a catalyst by itself.
atlers the position of equilibrium in a reversible reaction.
increases the number of active centres by increasing the unevenness of catalyst surface and by creating discontinuities in the crystals.
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.
The rate constant of a reaction is a function of the
time of reaction.
temperature of the system.
extent of reaction.
initial concentration of the reactants.
temperature of the system.
Mean residence time is equal to the space time, when
the feed rate is measured at temperature and pressure in the reactor.
the temperature, pressure and the density of reaction mixture remains constant throughout the reactor.
there is no change in number of moles in gaseous reaction.
all (a), (b) and (c).
all (a), (b) and (c).
If ‘n’ is the order of reaction, then unit of rate constant is
1/(time)(concentration)^n - 1
(time)^-1 (concentration)^n - 1
(time)^n - 1 (concentration)
none of these
1/(time)(concentration)^n - 1
Batch process is preferred over continuous process, when the
product yields and quality can not be achieved in continuous process, because of long residence time.
sales demand of product is not steady.
same equipment can not be used for several processes of the same nature.
all (a), (b) & (c)
all (a), (b) & (c)
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.
0
1
2
3
3
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
higher in CSTR
same in both the reactors
data insufficient; can’t be predicted
higher in P.F. reactor
For any reaction, we may write conversion as a function of
time
temperature
concentration
all (a), (b) & (c)
all (a), (b) & (c)
The use of space time is preferred over the mean residence time in the design of a/an
batch reactor
ideal tubular-flow reactor
slurry reactor
CSTR
ideal tubular-flow reactor
space time preferred - ideal tubular-flow
Autocatalytic reactions are best carried out in a
CSTR
CSTR in series
plug flow reactor
recycle reactor
recycle reactor
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
2/3
5/8
1/3
3/8
5/8
2AB 80% 20% 50% 5/8
A batch reactor suffers from following disadvantage.
Poor product quality control.
High labour and handling cost.
High shutdown time requirement for emptying, cleaning and refilling.
All (a), (b)and(c).
All (a), (b)and(c).
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.
of different sizes.
of such size that the ratio of their volumes is < 5.
none of these.
equal in size.
Half life period of a chemical reaction is proportional to CA0-1 , if the reaction is of __________ order.
first
zero
second
third
second
The irreversible reaction, X –> Y, is the special case of the reversible reaction, X <–>Y, in which the
equilibrium constant is infinite.
fractional conversion of ‘A’ at equilibrium is unity.
concentration of ‘A’ at equilibrium is zero.
all (a), (b) and (c).
all (a), (b) and (c).
The equilibrium constant K of a chemical reaction depends on
temperature only.
pressure only.
temperature and pressure.
ratio of reactants.
temperature only.
The reaction rate almost gets doubled for 10 C rise in temperature. This is due to the fact that the
increased temperature reduces the activation energy.
fraction of molecules having threshold energy increases.
collision frequency increases.
value of threshold energy decreases.
fraction of molecules having threshold energy increases.
Which of the following is not a unit of reaction rate ?
Moles for med/(surface of catalyst) (time)
Moles formed/volume of reactor) (time)
Mole formed/volume of catalyst) (time)
None of these
None of these
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 ?
Langmuir’s assumption applies to every adsorbed layer.
There is no dynamic equilibrium between successive layer.
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.
none of these.
There is no dynamic equilibrium between successive layer.
not BET no dynamic
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
5, 10, 15
10, 5, 15
10, 15, 5.
15, 10, 5
5, 10 and 15 = 15, 10, 5
The following half life data are available for the irreversible liquid phase reaction A products.
Initial Concentrations (K.mol/m^3): 2 and 8 and Half-lifes: 2 and 1, respectively. The overall order of reaction is
0.5
1
1.5
2
1.5
A non-catalytic chemical reaction of the type A –+Z,K1–> B –+Z,K2–> C –+Z,K–> D is called a __________ reaction.
parallel
series
series-parallel
none of these
series-parallel
The unit of frequency factor in Arhenious equation is
same as that of rate constant.
same as that of activation energy.
dimensionless.
none of these.
same as that of rate constant.
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
decreases
remains same
increases linearly
increases
Reaction of benzene with chlorine gas to produce tri-chlorobenzene exemplifies a/an __________ reaction.
elementary
parallel
consecutive
none of these
consecutive
For the gaseous reaction 2A –> B, where the feed consists of 50 mole % A and 50 mole % inerts, the expansion factor is
1
-0.5
-0.25
0
-0.25
The molecularity and the order of reaction respectively, for the hydrolysis of methyl acetate in presence of acids are
2 & 1
11 & 2
2 && 2
1 & 1
2 & 1
The irreversible reaction is a special case of reversible reaction, if the
equilibrium constant is 1.
conversion of the reactant at equilibrium condition is zero.
reactant concentration at equilibrium condition is zero.
all (a), (b) and (c).
reactant concentration at equilibrium condition is zero.
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
6
3
7/3
7
V/1 = Cao Xa/kCao(1-Xa) = Xa/k(1-Xa)
Xa = 1-Ca/Cao = 1-0.5/2 = 0.75.
V = 0.75/kx0.25 = 3/k —— (1).
V2/3 = Xa/k(1-Xa).
Xa = 1-Ca/Cao = 1-0.5/4 = 0.875.
V2/3 = 0.875/k(0.125) = 7/k ——(2).
Dividing (2) by (1),
(V2/3)/V = (7/k)/(3/k).
V2/3V = 7/3.
V2 = 7V.
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
low temperature in a CSTR.
high temperature in a CSTR.
low temperature in a PFR.
high temperature in a PFR.
high temperature in a PFR.
In an ideal mixed reactor (at steady state), the
space time is equivalent to holding time for constant density systems.
composition throughout the reactor remains same.
exit stream has the same composition as the fluid within the reactor.
all (a), (b) and (c).
all (a), (b) and (c).
The knowledge of initial concentration and rate constant is necessary to determine the half life time of a reaction of __________ order.
zero
first
second
none of these
second
Which of the following factors control the design of a fluid-solid reactor ?
Reaction kinetics for single particle,
Size distribution of solids beingtreated.
Flow patterns of solids and fluid in the reactor.
All (a), (b) and (c).
All (a), (b) and (c).
A Catalyst
increases the equilibrium concentration of the product.
changes the equilibrium constant of the reaction.
shortens the time to reach the equilibrium.
none of these.
shortens the time to reach the equilibrium.
The synthesis of proteins and metabolism in biological objects occur in the presence of biocatalyst called
a ferment or an enzyme
haemoglobin
fungi
none of these
fungi
synthesis of proteins biocatalyst fungi
Pick out the wrong statement.
A particular chemical reaction is more temperature sensitive at low temperatures.
A very high value of equilibrium constant, K (K»_space; 1) indicates that the reaction is practically irreversible in nature.
The intercept of the Arrhenious plot is called the ‘activation energy’.
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’.
Kinetics of a catalytic reaction can be best studied on a/an __________ reactor.
mixed
integral (plug flow)
differential (flow)
either (a), (b) and (c).
either (a), (b) and (c).
In case of a __________ reactor, the composition in the reactor and at the exit of the reactor is the same.
semi-batch
tubular
batch
back-mix
back-mix
Exothermic reactions are best carried out in
a CSTR.
CSTR in series.
a plug flow reactor followed by CSTR.
CSTR followed by a plug flow reactor.
CSTR followed by a plug flow reactor.
What is the order of chemical reaction A + B + C –K–> D , if itis found that the reaction rate doubles on doubling the concentration of B and also the reaction rate doubles when the concentrations of both A & B were doubled and quandrupled when the concentrations of both B & C were doubled ?
1
2
3
4
2
Reactions with high activation energy are
very temperature sensitive
temperature insensitive
always irreversible
always reversible
very temperature sensitive
If n = overall order of a chemical reaction. a = initial concentration of reactant. t = time required to complete a definite fraction of the reaction. Then pick out the correct relationship.
t is proportional to 1/a^n
t is proportional to 1/a^n-1
t is proportional to 1/a^n+1
t is proportional to a^n
t is proportional to 1/a^n-1
In case of a/an __________ chemical reaction, conversion increases with the rise in temperature.
reversible exothermic
irreversible exothermic
irreversible endothermic
reversible endothermic
reversible endothermic
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.
after every 5 hours, reactor is being filled with the feed.
cent per cent conversion can be achieved in at least 5 hours.
a fixed conversion of a given batch of feed takes 5 hours.
five reactor volumes of feed (at specified conditions) are being fed into the reactor per hour.
With increase in initial concentration, the fractional conversion of a first order reaction in a given time
increases
decreases
remains constant
unpredictable
remains constant
The rate of reaction of a/an __________ reaction is not affected by temperature rise.
autocatalytic
photochemical
consecutive
zero order.
photochemical
With an increase in pressure in gaseous phase chemical reactions, the fractional conversion __________ when the number of moles decreases.
increases
decreases
remains unaffected
unpredictable from the data
increases
Half-life period for a first order reaction is __________ the initial concentration of the reactant.
directly proportional to
inversely proportional to
independent of
none of these
independent of
Carbon particles accummulated on the catalyst used in the gas oil cracking lies in the category of __________ poison.
deposited
chemisorbed
selectivity
stability
deposited
carbon on catalyst deposited poison
The order of the chemical reaction, 2A + B –K–> C, whose rate equation is given as -rA= KCA2. CB is
0
1
2
3
3
What is the dispersion number for a plug flow reactor ?
0
infinite
1
-1
0
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 high P and high T.
at low P and high T.
at low P and low T.
at high P and low T.
at low P and low T.
The catalytic converter for conversion of SO2 to SO3 by contact process should have a feed with SO2 content between
2-5%
7-10%
12-15%
20-25%
7-10%
If the pore diffusion controls in a catalytic reaction, the apparent activation energy Ea is equal to
the intrinsic activation energy E.
(E + ED) where ED is activation due to diffusion.
(E + ED)/2
ED/2
ED/2
With increase in K2/K1 in case of a unimolecular type elementary reactions A –K1–> R –K2–> S , the fractional yield of ‘R’ in mixed reactor (for a given conversion of ‘A’)
decreases
increases
increases linearly
remains same
decreases
Collision theory gives the rate constant for bimolecular reaction as
K α √T.e^-E/RT
K α e^E/RT
K α e^-E/RT
none of these
K α e^-E/RT
typo error
arrhenius → K α e^-E/RT
transition state → K α T . e^-E/RT
collision → K α √T. e^-E/RT
just memorize the typo answer
collision - bimolecular - e^-E/RT
Find a mechanism that is consistent with the rate equation and reaction given below:
2A + B –> A2B, ( - rA) = k.CA.CB
A + B <–> AB ; AB + A –>A2B
A + B –> AB;AB + A –> A2B
A + A –> AA;AA + B –> A2B
A + A <–> AA;AA + B –> A2B
A + A <–> AA;AA + B –> A2B
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.
1
3
1/3
32
3
The temperature dependence of reaction rate constant (K) by Arhenius law is given by
K α e^-E/RT
K α e^E/RT
K α T . e^-E/RT
K α √T . e^-E/RT
K α e^-E/RT
arrhenius → K α e^-E/RT
transition state → K α T . e^-E/RT
collision → K α √T . e^-E/RT
For a __________ order chemical reaction, A + B –K–> C , the fractional conversion of reactant ‘A’ is proportional to time.
zero
first
second
third
zero
Velocity of a chemical reaction
decreases with increase in temperature.
increases with increase of pressure of reactants for all reactions.
decreases with increase of reactant concentration.
none of these.
none of these.
Backmixing is most predominant in
a well stirred batch reactor.
a plug-flow reactor.
a single CSTR.
CSTR’s connected in series.
a single CSTR.
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
increases
remains unaltered
changes unpredictably.
decreases
Fluidised bed reactor is characterised by
uniformity of temperature.
comparatively smaller equipment.
very small pressure drop.
absence of continuous catalyst regeneration facility.
uniformity of temperature.
In which of the following gaseous phase reversible reactions, the product yield can not be increased by the application of high pressure ?
N2 + O2 <–> 2NO
PCl3 + Cl2 <–> PCl5
N + 3H2 <–> 2NH3
2SO2 + O2 <–> 2SO3
N2 + O2 <–> 2NO
Space time equals the mean residence time
when the density of the reaction mixture is constant.
for large diameter tubular reactor.
for narrow diameter tubular reactor.
for CSTR.
when the density of the reaction mixture is constant.
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.
4
8
12
16
16
1st order 8 minutes 75% conversion 16 minutes
Rate constant ‘k’ and absolute temperature ‘T’ are related by collision theory (for bimolecular) as
k ∝ T^1.5
k ∝ exp(-E/RT)
k ∝ √T
k ∝ T
k ∝ √T
collision √T
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
60
75
90
100
75
What is the dispersion number for a CSTR?
0
1
< 1
infinite
infinite
Rate of a chemical reaction is independent of the concentration of the reactants for a __________ reaction.
zero order
third order
consecutive
none of these
zero order
With increase in temperature, the rate constant obeying Arhenious equation
increases.
decreases.
decreases exponentially.
can either increase or decrease ; depends on the frequency factor.
increases.
Bulk diffusion in catalyst pore __________ with increase in pressure.
increases
decreases
remains unchanged
increases exponentially
decreases
Pick out the correct statement.
A chemical reaction accompanied by absorption of heat is called an exothermic reaction.
A chemical reaction accompanied by evolution of heat is called an endother-mic reaction.
The rate constant for a first order reaction does not change on changing the concentration units.
Chemical equilibrium state is dynamic in nature.
The rate constant for a first order reaction does not change on changing the concentration units.
The concentration of A in a first order reaction, A –> B, decreases
linearly with time.
exponentially with time.
very abruptly towards the end of the reaction.
logarithmically with time.
exponentially with time.
The equilibrium constant of chemical reaction __________ in the presence of catalyst.
increases
decreases
remains unaffected
can either increase or decrease (depends on the type of catalyst)
remains unaffected
The order of a chemical reaction is
an experimentally determined quantity.
always equal to the total stoichiometric number of reactants.
never fractional.
none of these.
an experimentally determined quantity.
A chemical reaction occurs, when the energy of the reacting molecules is __________ the activation energy of reaction.
less than
equal to
more than
equal to or more than
equal to or more than
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
0.16
0.144
0.152
0.136
0.144
Catalyst is a substance, which __________ chemical reaction.
increases the speed of a
decreases the speed of a
can either increase or decrease the speed of a
alters the value of equilibrium constant in a reversible
can either increase or decrease the speed of a
The residence time distribution of an ideal CSTR is
1/T exp (-t/T)
T exp (-t/T)
exp (-t/T)
1/T (-t/T)
exp (-t/T)
A rise in temperature
normally tends to increase the reaction rate.
does not affect a catalysed reaction.
does not affect photo-chemical reaction rates.
all (a), (b) and (c).
all (a), (b) and (c).
The enzyme which can catalyse the conversion of glucose to ethyl alcohol is
invertase
maltase
diastase
zymase
zymase
For reaction, P + 2Q –>3R, molar rate of consumption of P is
double of that of Q.
same as that of Q.
half of that of Q.
2/3rd of that of Q.
half of that of Q.
If pore diffusion is the controlling step in a solid catalysed reaction, the catalyst
porosity is very important.
porosity is of less importance.
internal surface area is utilised efficiently.
none of these.
porosity is of less importance.
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
0.5
0.425
data insufficient to calculate
0.875
first order three times half life 0.875
In case of unimolecular type elementary reaction, A –K1–> B –K2–> C , plug flow reactor as compared to mixed reactor is
more
same
less
unpredictable
more
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
1/3
1/9
3
1/2
1/3=1/9^n,
9^n= 3,
(3)^2n= 3.
2n=1
And n=1/2.
The first order series reaction A –k1–> B –k2–> C is conducted in a batch reactor. The initial concentrations of A, B and C (CA0, CB0, CC0 respectively) are all non-zero. The variation of CB with reaction time will not show a maximum, if
k2 CB0 > k1 CA0
k CA0 > k2.CB0
CB0 > CA0
CA0 > CB0
k2 CB0 > k1 CA0
A second order reaction of the form A + B –> C is called a pseudo-first order reaction, when
CA0 = CB0
CA0 > CB0
CB0 > CA0
CB0 ≥ CB0
CB0 ≥ CB0
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.
Transition state theory approaches the problem of calculating reaction rates by concentrating on the idea of activated complexes.
According to the penetration theory, the mass transfer co-efficient decreases, if the exposure time of an eddy to the solute decreases.
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.
wrong According to the penetration theory…
Effectiveness factor (E) of a catalyst pellet is defined as E = actual rate within pore of the catalyst/rate if not snowed by pore diffusion , Effectiveness factor for a first order reaction is given by (where, T = Thiele modulus)
tan hT/T
tan T/T
tan hT/tan T
none of these
tan hT/T
E = tan hT/T
Inversion of cane sugar is an example of
unimolecular reaction with first order.
bimolecular reaction with second order.
bimolecular reaction with first order.
unimolecular reaction with second order.
bimolecular reaction with first order.
Pick out the correct statement.
A catalyst speeds up the forward reaction but slows shown the reverse reaction.
Addition of catalyst changes the equilibrium constant.
Pressure changes do not change the equilibrium concentrations.
The composition of equilibrium is changed by catalyst.
Pressure changes do not change the equilibrium concentrations.
correct pressure do not change equilibrium
In which of the following gaseous phase reactions, the equilibrium of the reaction remains unaffacted by pressure changes ?
2O3 <–> 3O2
N2 + O2 <–> 2NO
2NO2 <–> N2O4
2SO2 + O2 <–> 2SO3
N2 + O2 <–> 2NO
Integral method for analysing the kinetic data is used
when the data are scattered.
for testing specific mechanisms with simple rate expressions.
both (a) and (b).
none of these.
both (a) and (b).
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.
4
16
8
2
16
Rate of a chemical reaction is not affected by the
catalyst.
temperature.
reactant’s concentration.
number of molecules of reactants taking part in the reaction.
number of molecules of reactants taking part in the reaction.
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
independent of
inversely proportional to
proportional to the square of
proportional to
__________ resistance is not involved in the combustion of a carbon particle.
Gas film
Ash
Chemical reaction
none of these
Ash
In an ideal P.F.R. at steady state conditions
the composition of reactants remains constant along a flow path.
the conversion of the reactant varies from point to point along a flow path.
there is no lateral mixing of fluid.
there may be diffusion along the flow path.
the conversion of the reactant varies from point to point along a flow path.
B.E.T. method of finding out surface area of a catalyst, uses the extension of __________ isotherm.
Langmuir
Freundlich
Tempkin
none of these
Langmuir
In a chemical reaction, repesented by, A –k–> B , it is observed that the
(i) rate of reaction increases by a factor of 4 on doubling the concentration of the reactant.
(ii) rate of reaction increases by a factor of 9 on trebling the concentration of the reactant.
Then the rate of the reaction is proportional to(where, CA = contentration of the reactant)
CA
CA^2
CA^3
CA^4
CA^2
Which of the following holds good for an elementary reaction, X + 2Y –k1–> 3Z ?
The rate of disappearance of ‘Y’ is equal to the rate of appearance of ‘Z’.
The rate of disappearance of ‘Y’ is equal to the rate of disappearance of ‘X’.
Three times the rate of disappearance of ‘X’ is equal to the rate of appearance of ‘Z’.
The rate of disappearance of ‘X’ is equal to the rate of appearance of ‘Z’.
Three times the rate of disappearance of ‘X’ is equal to the rate of appearance of ‘Z’.
An example of autothermal reactor operation is
sulphur dioxide oxidation
ethylene oxidation
benzene oxidation
ammonia synthesis
ethylene oxidation
For a packed bed reactor; the presence of a long tail in the residence time distribution curve is an indication of
ideal plug flow
bypass
dead zone
chanelling
dead zone
long tail - dead zone
Space time in flow reactor is
usually equal to the residence time.
the reciprocal of the space velocity.
a measure of its capacity.
both (a) and (b).
both (a) and (b).
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 reduced.
catalyst size is reduced or the catalyst diffusivity is increased.
catalyst size is increased or the catalyst diffusivity is reduced.
catalyst size is increased or the catalyst diffusivity is increased.
catalyst size is reduced or the catalyst diffusivity is increased.
Cold shot cooling is only practical when the feed temperature is __________ than the reaction temperature.
higher
much higher
lower
much lower
much lower
The preferred reacting system for oxidation of o-xylene to phthalic anhydride is
jacketted liquid phase CSTR.
jacketted steam heated multitubular reactor.
multitubular reactor with cooling.
multistage multitubular reactor with interstage cooling.
jacketted liquid phase CSTR.
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)
L(sqrt(K/D1))
1/L(sqrt(K/D1))
1
infinite
1/L(sqrt(K/D1))
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.
reaction.
external mass transfer.
none of the above.
diffusion within the pellet.
Following isothermal kinetic data are obtained in a basket type of mixed flow reactor for a porous catalyst. Determine the role of pore diffusion and external mass transfer processes.
kinetic data table
Strong pore diffusion control and mass transfer not controlling.
Both pore diffusion and mass transfer not controlling.
Both pore diffusion and mass transfer controlling.
Mass transfer controlling.
Strong pore diffusion control and mass transfer not controlling.
