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Chemical Engineering
Chemical Reaction Engineering
Quiz 7
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Q.1
The most unsuitable reactor for carrying out reactions in which high reactant concentration favours high yields is
Backmix reactor
Plug flow reactor
Series of CSTR
PFR in series
Q.2
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.
256
512
112
612
Q.3
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
Q.4
In case of physical adsorption, the heat of adsorption is of the order of __________ kcal/kg.mole.
100
1000
10000
100000
Q.5
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
Q.6
As the chemical reaction proceeds, the rate of reaction
Increases
Decreases
Remains same
May increase or decrease depending on the type of reaction
Q.7
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 of the above
Q.8
__________ is the response curve for a step input signal from a reactor.
S-curve
C-curve
I-curve
None of these
Q.9
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
Q.10
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
Q.11
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
Q.12
The rate constant of a chemical reaction increases by increasing the
Temperature
Pressure
Reactant's concentration
None of these
Q.13
Knudsen diffusion is directly proportional to
T
√T
1/√T
T₂
Q.14
BET apparatus is used to determine the
Specific surface of a porous catalyst
Pore size distribution
Pore diameter
Porosity of the catalyst bed
Q.15
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
Q.16
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.
8
16
1/8
1/16
Q.17
A balanced chemical reaction equation conforms to the law of
Conservation of mass
Avagadro's hypothesis
Gaseous volumes
None ofthese
Q.18
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.
First
Second
Third
Any
Q.19
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
Q.20
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
Q.21
What is the order of a chemical reaction whose rate is deter-mined by the variation of one concentration term only?
Zero
First
Second
Third
Q.22
Which of the following curves shows the effect of temperature on the extent of gas-solid adsorption at a given pressure?
Langmuir adsorption isotherm
Adsorption isobar
Freundlich adsorption isotherm
None of these
Q.23
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
Q.24
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
Q.25
For a solid catalysed chemical reaction, the effectiveness of solid catalyst depends upon the __________ adsorption.
Physical
Chemical
Both A and B
Neither A nor B
Q.26
When a catalyst increases the rate of forward reaction, the value of rate constant
Increases
Decreases
Remain same
Becomes infinite
Q.27
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
Q.28
A plug-flow reactor is characterised by
High capacity
Presence of axial mixing
Presence of lateral mixing
Constant composition and temperature of reaction mixture
Q.29
Pick out the correct statement
Reactions with high activation energies are very temperature sensitive
Chemical equilibrium is a static state
A photochemical reaction is catalysed by light
A chemical reaction occurs when the energy of the reacting molecule is less than the activation energy of the reaction
Q.30
In a CSTR __________ varies with time.
Reaction rate
Concentration
Both A & B
Neither A nor B
Q.31
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 >> 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
Q.32
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
Q.33
The fractional volume change of the system for the isothermal gas phase reaction, A 3B , between no conversion and complete conversion is
0.5
1
2
3
Q.34
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 of the above
Q.35
Effectiveness factor of a catalyst pellet is a measure of the __________ resistance.
Pore diffusion
Gas film
Chemical reaction
None of these
Q.36
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
Q.37
The excess energy of the reactants required to dissociate into products is known as the __________ energy.
Thermal
Activation
Threshold
Binding
Q.38
The rate constant of a chemical reaction decreases by decreasing the
Pressure
Concentration of reactants
Temperature
Duration of reaction
Q.39
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
Q.40
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
Q.41
A first order reaction requires two unequal sized CSTR. Which of the following gives higher yield ?
Large reactor followed by smaller one
Smaller reactor followed by larger one
Either of the arrangement A or B will give the same yield
Data insufficient, can
Q.42
Enzymes are destroyed, when the
Temperature is very high
Reactant's concentration is very high
Reactant's concentration is very low
Reaction rate is independent of the reactant's concentration
Q.43
B.E.T. method of finding out surface area of a catalyst, uses the extension of __________ isotherm.
Langmuir
Freundlich
Tempkin
None of these
Q.44
Which of the following is the most suitable for very high pressure gas phase reaction?
Batch reactor
Tubular flow reactor
Stirred tank reactor
Fluidised bed reactor
Q.45
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
Q.46
Radioactive decay follows __________ order kinetics.
First
Second
Third
Zero
Q.47
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.
32
8
12
16
Q.48
For a tubular reactor with space time 'τ' and residence time 'θ', the following statement holds good.
τ and θ are always equal
τ = θ , when the fluid density changes in the reactor
τ = θ , for an isothermic tubular reactor in which the density of the process fluid is constant
τ = θ , for a non-isothermal reactor
Q.49
A catalyst is said to be a negative catalyst, ifit
Retards the rate of reaction
Reduces the value of equilibrium constant
Does not initiate the reaction
All of the above
Q.50
For a zero order chemical reaction, the
Half life period is directly proportion to the initial concentration of the reac-tants
Plot of products concentration with time is a straight line through the origin
Products concentration increases linerarly with time
All of the above
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