Chemical Reaction Engineering Flashcards
Which of the following will give maximum gas conversion ?
- Fixed bed reactor.
- Fluidised bed reactor.
- Semi-fluidised bed reactor.
- Plug-flow catalytic reactor.
Semi-fluidised bed reactor.
__________ explains the mechanism of catalysis.
- Activated complex theory
- Collision theory
- Thermodynamics
- None of these
Activated complex theory
From among the following, choose one which is not an exothermic process.
- Methanol synthesis
- Catalytic cracking
- Ammonia synthesis
- Oxidation of sulphur
Catalytic cracking
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
2
A catalyst
- initiates a reaction.
- lowers the activation energy of reacting molecules.
- is capable of reacting with any one of the reactants.
- can not 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 K→ C , if the rate of formation of ‘C’, increases by a factor of 2.82 on doubling the concentration of ‘A’ and increases by a factor of 9 on trebling the concentration of ‘B’?
- 7/2
- 7/4
- 5/2
- 5/4
7/2
For high conversion in a highly exothermic solid catalysed reaction, use a __________ bed reactor.
- fixed
- fluidised bed reactor followed by a fixed
- fixed bed reactor followed by a fluidised
- fluidised
fluidised 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.
- 8
- 12
- 16
- 32
16
A first order reaction requires two equal sized CSTR. The conversion is
- less when they are connected in series.
- more when they are connected in series.
- more when they are connected in parallel.
- 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.
- 100
- 1000
- 10000
- 100000
1000
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
backmix reactor
Pick out the wrong statement pertaining to space velocity of flow reactors.
- The unit of space velocity is (time)-1 .
- 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.
- The space velocity of 3 hr^-1 means that one third reactor volume of feed at specified conditions are being fed into the reactor.
- none of these.
The space velocity of 3 hr^-1 means that one third reactor volume of feed at specified conditions are being fed into the reactor.
A reactor is generally termed as an autoclave, when it is a
- high pressure batch reactor.
- atmospheric pressure tank reactor.
- high pressure tubular reactor.
- atmospheric pressure CSTR.
high pressure batch reactor.
6 gm 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 ?
- 100%
- 95%
- 75%
- 20%
95%
The rate constant of a chemical reaction decreases by decreasing the
- pressure
- concentration of reactants
- temperature
- duration of reaction
temperature
Reaction rate equation for the reaction,
R + 2S → X + Y is -dCR/dt = K.Cr.Cs^2
If S at is present in large excess, what is the order of this reaction?
- zero
- one
- two
- three
one
Rate of a gaseous phase reaction is given by, dpA/dt = K.p^2A. The unit of rate constant is
- (atm)^-1
- (hr)^-1
- (atm)^-1.(hr)^-1
- atm.(hr)^-1
(atm)^-1.(hr)^-1
__________ is the response curve for a step input signal from a reactor.
- S-curve
- C-curve
- I-curve
- none of these
S-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
- pressure
- temperature
- both (a) & (b)
- neither (a) nor (b)
temperature
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
Tubular flow reactor
The reaction between oxygen and organic material is a/an __________ reaction.
- exothermic
- endothermic
- biochemical
- photochemical
exothermic
With decrease in temperature, the equilibrium conversion of a reversible endother-mic reaction
- decreases
- increases
- remains unaffected
- increases linearly with temperature
decreases
In an exothermic chemical reaction, the reactants compared to the products have
- higher temperature
- more energy
- less energy
- same energy.
more energy
For a reaction of the type,
V –(K1)> X –(K2)> Y –(K3)> Z,
the rate of reaction (- rx) is given by
- (K1+K1)Cx
- (K1+K2+K3)Cx
- K1Cv - K2Cx
- (K1-K2)Cx
K1Cv - K2Cx
In a consecutive reaction system
A–(E1)>B–(E2)>C
when E1 is much greater than E2, the yield of B increases with the
- increase of temperature.
- decrease of temperature.
- increase in initial concentration of A.
- 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
- decreases.
- increases.
- is at the highest allowable temperature throughout.
- 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
- 8987°K
- 9210°K
- 8764°K
- 8621°K
9210°K
A batch reactor is suitable for
- achieving cent percent conversion of reactants into products.
- large scale gaseous phase reactions.
- liquid phase reactions.
- obtaining uniform polymerisation products in highly exothermic reactions.
liquid phase reactions.
For a heterogeneous catalytic reaction
- free energy of activation is lowered in the presence of catalyst, which remains unchanged at the end of reaction.
- a relatively small amount of catalyst can cause the conversion of large amount of reactants which does not mean that catalyst concentration is important.
- the catalyst does not form an intermediate complex with the reactant.
- 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
- increase in the number of effective collisions.
- decrease in activation energy.
- increase in the average kinetic energy of the reacting molecules.
- none of these.
decrease in activation energy.
A catalyst loses its activity due to
- loss in surface area of the active component.
- agglomeration of metal particles caused by thermal sintering of the solid surface.
- covering of the catalytic active sites by a foregin substance.
- all (a), (b) and (c).
all (a), (b) and (c).
‘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
any
For the irreversible elementary reactions in parallel viz
X –(k2)> Y; X –(k1)>Z,
the rate of disappearance of ‘X’ is equal to
- CA(K1+K2)
- CA(K1 + K2)/2
- CA . K1/2
- CA . K2/2
CA(K1+K2)
For an isothermal variable volume batch reactor, the following relation is applicable for a first order irreversible reaction.
- XA = k . t
- CAo/(1+εxa) (dxa/dt) = k
- -ln(1 - XA) = kt
- εA . ln (1 - XA) = k . t
CAo/(1+εxa) (dxa/dt) = k
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 (a), (b) and (c).
all (a), (b) and (c).
BET apparatus
- measures the catalyst surface area directly.
- operates at very high pressure.
- is made entirely of stainless steel.
- none of these.
none of these.
Radioactive decay follows __________ order kinetics.
- first
- second
- third
- zero.
first
The excess energy of reactants in a chemical reaction required to dissociate into products is termed as the __________ energy.
- activation
- potential
- binding
- threshold
activation
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)
chemical
Pick out the correct statement.
- In catalytic reactions, the catalyst reacts with the reactants.
- A catalyst initiates a chemical reaction.
- A catalyst lowers the activation energy of the reacting molecules.
- A catalyst can not be recovered chemi cally 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
- 0
- 1
- 2
- 3
2
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.
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
- 0
- 1
- 2
- 3
2
Sulphuric acid is used as a catalyst in the
- hydrogenation of oils.
- gas phase oxidation of SO2 in chamber process.
- alkylation of hydrocarbons.
- none of these.
alkylation of hydrocarbons.
Fractional conversion __________ with increase in pressure for ammonia synthesis reaction i.e., N2 + 3H2 ⇌ 2NH3.
- increases
- decreases
- remains unchanged
- unpredictable from the data
increases
Pick out the wrong statement.
- The vessel dispersion number (D/UL) for plug flow and mixed flow approaches zero and infinity respectively.
- 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.
- Mixed reactor is always smaller than the plug flow reactor for all positive reaction orders for a particular duty.
- In an ideal tubular flow reactor, mixing takes place in radial direction and there is no mixing in logitudinal direction.
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
- decreases the energy barrier for reaction.
- increases the activation energy.
- decreases the molecular collision diameter.
- 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.
- both conversion as well as concentration are same
- conversion in both will be the same but concentrations will be different
- both the conversion as well as concentrations will be different
- 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
- > 1
- < 1
- 1
- 0
- 1
In an ideal tubular-flow reactor
- there is no mixing in longitudinal direction.
- mixing takes place in radial direction.
- there is a uniform velocity across the radius.
- all (a), (b) and (c).
all (a), (b) and (c).
At a given value of E/R (ratio of activation energy and gas constant), the ratio of the rate constants at 500°K and 400°K is 2, if Arrhenious law is used. What will be this ratio, if transition state theory is used with the same value of E/R?
- 1.6
- 2
- 2.24
- 2.5
2.5
__________ is the controlling step in a highly temperature sensitive fluid-solid non-catalytic reaction.
- Gas film diffusion
- Ash diffusion
- Chemical reaction
- none of these
Chemical reaction
An autothermal reactor is
- most suitable for a second order reaction.
- most suitable for a reversible reaction.
- completely self-supporting in its thermal energy requirements.
- isothermal in nature.
completely self-supporting in its thermal energy requirements.
The rate constant of a first order reaction depends on the
- concentration of the reactant.
- temperature.
- concentration of the product.
- time.
temperature.
A reaction in which one of the products of reaction acts as a catalyst is called a/an __________ reaction.
- catalytic
- autocatalytic
- photochemical
- 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
- ∞
- 0
- 1
- > 1
1
Which of the following will favour the reverse reaction in a chemical equilibrium reaction ?
- Increasing the concentration of one of the reactants.
- Increasing the concentration of one or more of the products.
- Removal of at least one of the products at regular interval.
- 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.
- autocatalytic
- irreversible
- reversible endothermic
- reversible exothermic
reversible endothermic
Effective diffusivity (DE) in a catalyst pellet is related to molecular diffusivity (DN) and Knudsen diffusivity (DK) as
- DE = DM + DK
- 1/De = 1/Dn + 1/Dk
- DE = DM . DE
- DE = DN / DE
1/De = 1/Dn + 1/Dk
A photochemical reaction is __________ light.
- initiated by
- accompanied with emission of
- catalysed by
- used to convert heat energy into
initiated by
Pick out the wrong statement.
- In a batch reactor, which is exclusively used for liquid phase reactions; temperature pressure and composition may vary with time.
- In a semi-batch reactor, one reactant is charged batchwise, while the other reactant is fed continuously.
- In a continuous flow reactor, uniform concentration can not be maintained throughout the vessel even in a well agitated system.
- In a continuous flow reactor, both the reactants and the products flow out continuously.
In a continuous flow reactor, uniform concentration can not be maintained throughout the vessel even in a well agitated system.
In a/an __________ reactor, there is exchange of heat with the surroundings with sizeable temperature variation.
- adiabatic
- isothermal
- non-adiabatic
- none of these.
non-adiabatic
‘Unreacted core model’ represents the reaction involving
- combustion of coal particles.
- roasting of sulphide ores.
- manufacture of carbon disulphide from elements.
- none of these.
roasting of sulphide ores.
For a vapour phase catalytic reaction (A + B → P) which follows the Ridel mechanism and the reaction step is rate controlling, the rate of reaction is given by (reaction rate is irreversible, product also absorbs).
- -rA = k.PA.PB / 1+.KA.PA+KP.PP
- -rA = k.PA²-k1.PP / 1+KA.PA+KP.PP
- -rA = k.PA.PB / 1.KA.PB+KB.PB.KP.PP
- -rA = k.PA.PB / 1+KA.PA
- -rA = k.PA.PB / 1+.KA.PA+KP.PP
If a solid-gas non-catalytic reaction occurs at very high temperature, the rate controlling step is the __________ diffusion.
- film
- ash layer
- pore
- none of these
film
The units of frequency factor in Arhenious equation
- are the same as those of the rate constant.
- depend on the order of the reaction.
- depend on temperature, pressure etc. of the reaction.
- 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 ?
- Surface chemical reaction
- Adsorption
- Desorption
- None of these
None of these
For a series of reactions A –(k1)> B –(K2)> C having k1 «_space;k2, the reaction system can be approximated as
- A –(k1)> B
- A –(k2)> B
- A –(k2)> C
- A –(k1)> C
A –(k1)> C
At a given temperature, K1, K2 and K3 are equilibrium constants for the following reactions 1, 2, 3 respectively.
CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g),
CO(g) + H2O(g) ⇌ CO2(g) + H2(g)
CH4(g) + 2H2O(g) ⇌ CO2(g) + 4H2(g)
Then K1, K2 and K3 are related as:
- K3 = K1.K2
- K3 = (K1.K2)^0.5
- K3(K1+K2)/2
- K3 = (K1.K2)^2
K3 = K1.K2
In case of __________ reactions, the reaction rate does not decrease appreciably as the reaction proceeds.
- catalytic
- parallel
- series
- auto catalytic
auto catalytic
For nearly isothermal operation involving large reaction time in a liquid-phase reaction, the most suitable reactor is a __________ reactor.
- stirred tank
- tubular flow
- batch
- fixed bed
stirred tank
What is the Thiele modulus of the solid catalysed first order reaction, X–(k)> Y , if the pore diffusion offers negligible resistance to reaction ?
- < 5
- < 0.5
- > 1
- 5
- < 0.5
B.E.T. method can be used to determine the __________ of a porous catalyst.
- solid density
- pore volume
- surface area
- 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/litre to 50 gm moles/litre is same as that required to reduce it from 2 gm moles/litre to 1 gm mole/litre in the same volume. Then the order of this reaction is
- 0
- 1
- 2
- 3
1
Which of the following is an independent variable for a batch tank reactor with uniform concentration and temperature ?
- Time
- Useful volume of the tank
- Diameter of the reactor
- None of these
Time
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
16
In a reversible chemical reaction having two reactants in equilibrium, if the concentration of the reactants are doubled, then the equilibrium constant will
- remain the same
- be halved
- also be. doubled
- become one fourth
remain the same
The equilibrium constant of a catalytic chemical reaction __________ due to the presence of a catalyst.
- increases
- decreases
- remains unaffected
- unpredictable from the data
remains unaffected
The rate constant of a chemical reaction increases by increasing the
- temperature
- pressure
- reactant’s concentration
- none of these
temperature
The catalytic activity of enzymes is due to their capacity to lower the __________ energy.
- activation
- potential
- kinetic
- none of these
activation
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’t be predicted.
Either of the arrangement (a) or (b) will give the same yield.
Pick out the correct statement.
- A lower temperature favours the reaction of lower activation energy.
- The dispersion number for a reactor/vessel is uL/D.
- The rate controlling step in a reaction involving many steps is the fastetst step.
- Pore volume and porosity of a catalyst is measured by Brunaver-Emmet-Teller (BET) technique.
A lower temperature favours the reaction of lower activation energy.
The effect of increasing pressure on the gaseous equilibrium of the reaction 2X+3Y ⇌ 3X+2Y indicates that
- pressure has no effect.
- backward reaction is favoured.
- forward reaction is favoured.
- none of these.
pressure has no effect.
If in the gaseous phase reaction, N2O4 ⇌ 2NO2, x is the part of N2O4 which dissociates, then the number of molecules at equilibrium will be
- (1 + x)
- (1 - x)
- (1 + x)^2
- (1 - x)^2
(1 + x)
A batch reactor is characterised by
- constant residence time.
- variation in extent of reaction and properties of the reaction mixture with time.
- variation in reactor volume.
- very low conversion.
variation in extent of reaction and properties of the reaction mixture with time.
When a catalyst increases the rate of forward reaction, the value of rate constant
- increases
- decreases
- remain same
- becomes infinite
increases
Rate determining step in a reaction consisting of a number of steps in series is the __________ step.
- fastest
- slowest
- intermediate
- 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 form 10 to 100°C.
- 256
- 512
- 112
- 612
512
A catalyst in a chemical reaction __________ free energy change in the reaction.
- increases
- decreases
- either (a) or (b); depends on the type of catalyst
- neither (a) nor (b).
either (a) or (b); depends on the type of catalyst
When all the limiting reactant is consumed in the reaction, the operational yield __________ the relative yield.
- is greater than
- is smaller than
- equals
- can be either greater or smaller than (depends on the type of reaction)
equals
The half life period of a first order reaction is
- always the same irrespective of the reaction.
- independent on initial concentration of the reactants.
- proportional to the initial concentration of reactants.
- half the specific rate constant.
independent on initial concentration of the reactants.
The catalyst in a second order reversible reaction increases the rate of the forward reaction
- and decreases that of backward reaction.
- and backward reaction equally.
- only.
- to a greater extent than that of the backward reaction.
and backward reaction equally.
Catalyst carriers
- have very high selectivity.
- increase the activity of a catalyst.
- provide large surface area with a small amount of active material.
- 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.
- 0.15
- 0.30
- 0.60
- 0.90
0.60
In flow reactors, the performance equations interrelate the rate of reaction to the
- feed rate.
- reactor volume,
- extent of reaction.
- all (a), (b) and (c).
all (a), (b) and (c).
Space velocity
- describes the extensive operating characteristics of a tubular flow reactor.
- is the maximum feed rate pre unit volume of reactor for a given conversion.
- is a measure of the ease of the reaction.
- all (a), (b) and (c)
all (a), (b) and (c)
The rate of the chemical reaction A B doubles as the concentration of A i.e.., CA is doubled. If rate of reaction is proportional to CAn, then what is the value of n for this reaction ?
- 0.5
- 1
- 0
- 2
1
A reaction which is catalysed by a base is catalysed by all substances which have a tendency to
- lose a proton
- gain a proton
- gain an electron
- none of these
gain a proton
For a homogeneous reaction of nth order, the dimension of the rate constant is given by
- l/(time)^n
- (concentration)^(1 - n)/(time)
- (concentration)^(n - 1)/(time)
- none of these
(concentration)^(1 - n)/(time)
The fractional volume change between no conversion and complete conversion, for the isothermal gas phase reaction, 2A R, is
- 0.5
- -0.5
- 1
- 1.5
-0.5
The reaction in which one of the products of reaction acts as a catalyst is called a/an __________ reaction.
- biochemical
- photochemical
- catalytic
- autocatalytic
autocatalytic
A typical example of an exothermic reversible reaction conducted at high pressure in industry is
- dehydration of ethanol.
- methanol synthesis.
- reformation of methane.
- polymerisation of ethylene.
dehydration of ethanol.
Study of chemical kinetics is the easiest in the case of __________ reactions.
- irreversible
- reversible
- surface
- side
irreversible
In autocatalytic reactions,
- one of the reactants acts as a catalyst.
- one of the products acts as a catalyst.
- catalysts have very high selectivity.
- no catalyst is used.
one of the products acts as a catalyst.
Semibatch reactor is preferred, when a/an
- a highly exothermic reaction is to be controlled.
- undersirable side reaction (at high concentration of one of the reactants) is to be avoided.
- a gas is to be reacted with liquid (e.g. hydrogenation of fat).
- all (a), (b), and (c).
all (a), (b), and (c).
For identical flow rate, feed composition and for elementary first order reactions, ‘N’ equal sized mixed reactors in series with a total volume ‘V’ gives the same conversion as a single plug flow reactor of volume ‘V’ for constant density systems. This is true, when the value of ‘N’ is
- 1
- > 1
- ∞
- ≥1
∞
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
first
Pick out the wrong statement.
- Visible radiation provides the necessary activation energy in photochemical reactions.
- The order and molecularity of a complex reaction may not be the same.
- For a second order reaction, the slope of the graph/plot between rate and (concentration) is equal to the rate constant (k).
- Molecularity of the reaction is always a whole number greater than zero.
The order and molecularity of a complex reaction may not be the same.
The rate at which a chemical substance reacts is proportional to its
- active mass
- equivalent weight
- molecular weight
- none of these
active mass
The exit age distribution of a fluid leaving a vessel (denoted by E) is used to study the extent of non-ideal flow in the vessel. The value of ∫(Edt),0 to ∞ is
- 0
- 1
- ∞
- √(2π)
1
A plug-flow reactor is characterised by
- high capacity.
- presence of axial mixing.
- presence of lateral mixing.
- constant composition and temperature of reaction mixture.
presence of lateral mixing.
Three plug flow reactors (PFR’s) of 4, 5 & 6 m3 volumes are arranged in two branches as shown below in the figure.
If the total feed rate is 300 tons/hr, then for the same conversion in each branch, the feed rate through branch II should be __________ tons/hr.
- 100
- 150
- 200
- 225
100
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.
τ = θ , for an isothermic tubular reactor in which the density of the process fluid is constant.
Rate of an autocatalytic chemical reaction is a function of
- temperature only.
- pressure only.
- composition only.
- all (a), (b) and (c).
all (a), (b) and (c).
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
Adsorption isobar
For an ideal mixed flow reactor (CSTR), the exit age distribution E(t) is given by
- a dirac delta function
- a step function.
- a ramp function.
- none of the above
none of the above
Fluid flow in a real packed bed can be approximated as __________ model.
- plug flow
- dispersion
- mixed flow
- tank in series
dispersion
The ‘E’ curve for a non-ideal reactor defines the fraction of fluid having age between t and t + dt
- at the inlet
- at the outlet
- in the reactor
- averaged over the inlet and outlet
at the outlet
To maximise the formation of R in the simultaneous reaction
A + B R , rR = 2CA^0.5.CB^2
A + B S , rS = 1.5 CA . CB
We should have
- low CA, low CB
- low CA, high CB
- high CA, low CB
- high CA, high CB
low CA, high CB
A reaction which is catalysed by an acid is also catalysed by any substance, which has a tendency to
- lose a proton.
- gain a proton.
- lose an electron
- none of these.
lose a proton.
A stirred tank reactor compared to tubular-flow reactor provides
- more uniform operating conditions.
- permits operation at the optimum temperature for a long reaction time.
- higher overall selectivity for a first order consecutive reaction.
- all (a), (b) and (c)
all (a), (b) and (c)
A chemical reaction, A → 3B, is conducted in a constant pressure vessel. Starting with pure A, the volume of the reaction mixture increases 3 times in 6 minutes. The fractional conversion is
- 0.33
- 0.5
- 1
- data insufficient, can’t be predicted
1
A catalyst inhibitor
- lessens its selectivity.
- may be useful for suppressing undesirable side reactions.
- is added in small quantity during the catalyst manufacture itself.
- all(a), (b) and (c).
all(a), (b) and (c).
In chamber process of sulphuric acid manufacture in industry, the gas phase oxidation of SO2 to SO3 is accomplished by a __________ reaction.
- non-catalytic homogeneous
- non-catalytic heterogeneous
- catalytic homogenous
- catalytic heterogeneous
catalytic homogenous
If the rate of a chemical reaction becomes slower at a given temperature, then the
- initial concentration of the reactants remains constant.
- free energy of activation is lower.
- entropy changes.
- free energy of activation is higher.
free energy of activation is higher.
The conversion XA and residence time data are collected for zero order liquid phase reaction in a stirred tank reactor. Which of the following will be a straight line ?
- XA Vs . τ
- XA Vs ln τ
- XA/(1 - XA)Vs τ
- XA(1 - XA)Vs τ
XA Vs . τ
The rate of the reaction, X → Y, quadruples when the concentration of ‘X’ is doubled. The rate expression for the reaction is, r = K Cx^n, the value of ‘n’ in this case will be
- 0
- 1
- 2
- 3
2
The value of steric factor ‘P’ in the equation k = PZe^(E/RT) usually ranges from
- 1.0 to 10^-8
- 1.1 to 10^2
- 0.1 to 0.9
- none of these
1.0 to 10^-8
For a zero order reaction, the concentration of product increases with the
- increase of reaction time.
- increase in initial concentration.
- total pressure.
- decrease in total pressure.
increase of reaction time.
Pick out the wrong statement.
- ‘Hold back’ is defined as the fraction of material that stays longer than the mean residence time.
- Study of non-ideal flow reactor is done experimentally by stimulus-response technique.
- For studying a chemical reaction, it is desirable to monitor the reactants during initial stages and the products during the final stages of reaction.
- A batch reactor can not be used to study the kinetics of catalytic reaction.
A batch reactor can not be used to study the kinetics of catalytic reaction.
Effectiveness factor of a catalyst pellet is a measure of the __________ resistance.
- pore diffusion
- gas film
- chemical reaction
- none of these
pore diffusion
The rate expression for a heterogenous catalytic reaction is given by, - rA = K.KA PA(1 + KA.PA + KR.PR), where K is surface reaction rate constant and KA and KR are absorption equilibrium constants of A and R respectively. If KR PR»_space; (1 + KA PA), the apparent activation energy EA is equal to (given E is the activation energy for the reaction and ΔHR and ΔHA are the activation energies of adsorption of R and A)
- E
- E + ΔHA
- E + ΔHA - ΔHR)
- ΔHA + ΔHR
E + ΔHA - ΔHR)
Given,
3H2 + CO = CH4 + H2O, KP = 10^1.84 and,
4H2 + CO2 = CH4 + 2H2O, KP = 10^1.17
the KP for the reaction CO + H2O = CO2 + H2 is
- 10^3.01
- 10^-0.67
- 10^-3.01
- 10^0.67
10^0.67
Differential method for analysing the kinetic data is used
- for testing complicated mechanisms.
- when the data are scattered.
- when rate expressions are very simple.
- none of these.
for testing complicated mechanisms.
In case of the irreversible unimolecular type, first order reaction, the fractional conversion at any time for constant volume system as compared to variable volume system is
- more
- less
- same
- either (a) or (b), depends on other factors
same
The reaction in which the rate equation corresponds to a stoichiometric equation, is called a/an __________ reaction.
- elementary
- non-elementary
- parallel
- autokinetic
elementary
The reaction A B is conducted in an isothermal batch reactor. If the conversion of A increases linearly with holding time, then the order of the reaction is
- 0
- 1
- 1.5
- 2
0
A first order gaseous phase reaction is catalysed by a non-porous solid. The kinetic rate constant and the external mass transfer co-efficients are k and kg respectively. The effective rate constant (keff) is given by
- keff = k + kg
- keff = (k+ kg)/2
- keff = (kkg)1/2
- 1/keff = 1/k + 1/kg
1/keff = 1/k + 1/kg
Arrhenious equation represents graphically the variation between the __________ and temperature.
- rate of reaction
- frequency factor
- rate constant
- activation energy
rate constant
__________ catalytic reaction is involved in the thermal cracking of gas oil.
- Homogeneous
- Homogeneous non
- Heterogeneous
- Heterogeneous non
Homogeneous
Variables affecting the rate of homogeneous reactions are
- pressure and temperature only.
- temperature and composition only.
- pressure and composition only.
- pressure, temperature and composition.
pressure, temperature and composition.
A chemical reaction occurs when the energy of the reacting molecules is __________ the activation energy of the reaction.
- less than
- equal to
- more than
- equal to or more than
equal to or more than
Which of the following resistances is not involved in a gas phase catalytic (gas-solid) reaction ?
- Ash resistance.
- Gas film and pore surface diffusion resistances for reactants.
- Surface phenomenon resistance.
- Gas film and pore surface diffusion resistances for products.
Ash resistance.
If the time required to change the concentration of reactant to half its original value is independent of the initial concentration, the order of reaction is
- zero
- one
- two
- three
one
A batch adiabatic reactor at an initial temperature of 373°K is being used for the reaction, A → B. Assume the heat of reaction is - 1kJ/mole at 373°K and heat capacity of both A and B to be constant and equal to 50J/mole.K. The temperature rise after a conversion of 0.5 will be
- 5°C
- 10°C
- 20°C
- 100°C
10°C
If CA is the quantity of reactants initially present, the quantity left after ‘n’ half periods will be equal to
- (CA/2)^n
- (1/2)^n × CA
- (CA/2)^(1/n)
- (CA)1/2n
(1/2)^n × CA
A photochemical reaction is
- accompanied with emission of light.
- catalysed by light.
- initiated by light.
- all (a), (b) & (c).
initiated by light.
The rate controlling step for the heterogeneous irreversible catalytic reaction A(g) + B(g) C(g) is the surface reaction of absorbed A with absorbed B to give adsorbed C. The rate expression for this reaction can then be written as (where, KA, KB and KC are the equilibrium constants and is the rate constant of the rate controlling step.)
- k.KA.PA.PB / (1 + KAPA + KBPB)
- k.KA.KB.PA.PB / (1 + KAPA + KBPB)
- k.KA.KB.PA.PB / (1 + KAPA + KBPB + KCPC)
- k.KA.KB.PA.PB / (1 + KAPA + KBPB + KCPC)^2
- k.KA.KB.PA.PB / (1 + KAPA + KBPB + KCPC)^2
The optimum performance for reactors operating in parallel is obtained when the feed stream is distributed in such a way, that the
- space time for each parallel line is same.
- space time for parallel lines is different.
- larger reactors have more space time compared to smaller ones.
- none of these.
space time for each parallel line is same.
A catalyst is said to be a negative catalyst, if it
- retards the rate of reaction.
- reduces the value of equilibrium constant.
- does not initiate the reaction.
- all (a), (b) and (c).
retards the rate of reaction.
For the non catalytic reaction of particles with surrounding fluid, the same needed to achive the same fractional conversion for particles of different unchanging sizes is proportional to the particle diameter, when the __________ is the controlling resistance.
- film diffusion
- diffusion through ash layer
- chemical reaction
- either (a), (b) or (c)
chemical reaction
Pure ethanol vapor is fed to a reactor packed with alumina catalyst, at the rate of 100 kmole / hr. The reactor products comprise: ethylene :95 kmole / hr, water vapour: 97.5 k mole / hr and diethyl ether :2.5 kmole/hr. The reactions occuring can be represented by:
C2H5OH C2H4 + H2O
2C2H5OH C2H5 - O - C2H5 + H2O
The percent conversion of ethanol in the reactor is
- 100
- 97.5
- 95
- 2.5
100
Pick out the wrong statement.
- The integral method of analysing kinetic data is used when the data is scattered.
- The differential method of analysing kinetic data requires more accurate or larger amounts of data.
- When the reaction rate is independent of temperature, the reaction is said to be of zero order.
- The ratio of volumes of plug flow reactor to that of mixed reactor is always less than one for identical feed composition, flow rate, conversion and for all positive reaction orders.
When the reaction rate is independent of temperature, the reaction is said to be of zero order.
The conversion for a second order, irreversible reaction (constant volume), , in batch mode is given by
- 1/(1+K2.CA0.t)
- (k2.CA0.t) / (1+k2.CA0.t)
- (k2.CA0.t)^2 / (1+k2.CA0.t)
- (k2.CA0.t) / (1+k2.CA0.t)^2
(k2.CA0.t) / (1+k2.CA0.t)
A backmix reactor
- is same as plug-flow reactor.
- is same as ideal stirred tank reactor.
- employs mixing in axial direction only.
- is most suitable for gas phase reaction.
is same as ideal stirred tank reactor.
Rate of a chemical reaction is not influenced by the
- catalyst
- temperature
- reactants concentration
- number of molecules of reactants taking part in a reaction
number of molecules of reactants taking part in a reaction
Pick out the wrong statement:
- Chemical reactions with high activation energy are very temperature sensitive.
- A flat velocity profile exists in a plug flow reactor.
- The residence time for all the elements of fluid in case of a P.F.R. need not be same.
- Half life of a reaction increases with increased initial concentration for reaction orders more than one.
The residence time for all the elements of fluid in case of a P.F.R. need not be same.
The reaction A B is conducted in an adiabatic plug flow reactor (PFR). Pure A at a concentration of 2 kmol/m3 is fed to the reactor at the rate of 0.01 m3 /s and at a temperature of 500 K. If the exit conversion is 20%, then the exit temperature (in k)is (Data: Heat of reaction at 298 K = - 50000 kJ/ kmole of A reacted Heat capacities CPA = CPB = 100kJ/kmole. K (may be assumed to be independent of temperature))
- 400
- 500
- 600
- 1000
600
Which of the following is not a theory of homogeneous reaction?
- Collision theory and activated complex theory
- Chain reaction theory
- Radiation hypothesis
- None of these
None of these
A first order homogeneous reaction of the type X Y Z (consecutive reaction) is carried out in a CSTR. Which of the following curves respectively show the variation of the concentration of X, Y and Z with time?
(graph - S4P4)
- I, II, III
- III, II, I
- III, I, II
- II, III, i
III, II, I
In a semi-batch reactor,
- mixing takes place in axial direction only.
- velocity of reaction can be controlled.
- condition similar to plug flow reactor exists.
- residence time is constant.
velocity of reaction can be controlled.
Which of the following is a controlling factor in very fast heterogeneous reaction ?
- Heat and mass transfer effects
- Pressure
- Temperature
- Composition of reactant
Heat and mass transfer effects
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.
temperature is very high,
For an autocatalytic reactor, the suitable reactor set up is
- P.F. reactors in series.
- CSTR in series.
- CSTR followed by P.F. reactor.
- P.F. reactor followed by CSTR.
CSTR followed by P.F. reactor.
Ionic reactions occur in
- solid state only
- liquid state only
- solutions
- any state
solutions
In a chemical reaction X +Y+Z –()k)> P, it is observed that the
(i) rate of formation of ‘P’ is doubled on doubling the concentration of ‘X’.
(ii) rate of formation of ‘P’ is quadrupled on doubling the concentration of ‘Y’.
(iii) doubling the concentration of ‘Z’ does not affect the rate of formation of ‘P’.
What is the order of the above chemical reaction?
- Zeroth order
- First order
- Second order
- Third order
Third order
The half life period of a first order reaction is given by (where, K = rate constant. )
- 1.5K
- 2.5 K
- 0.693/K
- 6.93 K
0.693/K
Half life period of a chemical reaction is
- the time required to reduce the concentration of the reacting substance to half its initial value.
- half of the space time of a reaction.
- half of the residence time of a reaction.
- none of these
the time required to reduce the concentration of the reacting substance to half its initial value.
In the gaseous phase ammonia formation reaction (N2 + 3H2 ⇌ 2NH3), the value of the equilibrium constant depends on the
- total pressure of the system.
- volume of the reactor.
- temperature.
- initial concentration of N2 and H2.
temperature.
Transition state theory relates the above quantities as
- k ∝ e^(-E/RT)
- k ∝ T.e^(E/RT)
- k ∝ T
- k ∝ T^(1.5)
k ∝ T.e^(E/RT)
Photochemical reaction rate does not depend significantly on temperature, because
- it is a reversible reaction.
- it is an exothermic reaction.
- the energy of reacting molecules exceeds the activation energy by absorption of light.
- none of these.
the energy of reacting molecules exceeds the activation energy by absorption of light.
A CSTR is to be designed in which an exothermic liquid phase first order reaction of the type, A → R, is taking place. The reactor is to be provided with a jacket in which coolant is flowing. Following data is given: CA0= 5 kmole/m^3 ; XA = 0.5; Feed temperature = reactor temperature = 40°C. Rate constant at 40°C = 1 min-1 ; (ΔH) = - 40kJ/mole; ρ = 1000kg/m3 CP = 4 J/gm.°C ; q = 10^-3 m^3/min (ρ and CP are same for the reactant and product streams). The amount of heat to be removed is
- 2/3 kW
- 1kW
- 5/3 kW
- 4kW
5/3 kW
According to the ‘law of mass action’, the rate of reaction is directly proportional to the
- equilibrium constant.
- volume of the reaction vessel.
- nature of the reactants.
- molar concentration of the reactants.
molar concentration of the reactants.
For an ideal gas mixture undergoing a reversible gaseous phase chemical reaction, the equilibrium constant
- is independent of pressure.
- increases with pressure.
- decreases with pressure.
- increases /decreases with pressure depending on the stoichiometric co-efficients of the reaction.
increases with pressure.
In the reversible reaction of the type, A + B ⇌ AB, in general
- both forward and backward reactions will be exothermic.
- neither of the reactions will be en-dothermic.
- the combination reaction will be exothermic, while the dissociation reaction will be endothermic.
- the combination reaction will be endothermic, while the dissociation reaction will be exothermic.
the combination reaction will be exothermic, while the dissociation reaction will be endothermic.
A batch reactor is
- suitable for gas-phase reactions on commercial scale.
- suitable for liquid phase reactions involving small production rate.
- least expensive to operate for a given rate.
- most suitable for very large production rate.
suitable for liquid phase reactions involving small production rate.
For a first order reaction carried out in a plug flow reactor, the space time is
- 1/K ln(C0/C)
- 1/K ln(C/C0)
- K ln(C0/C)
- K ln(C/C0)
1/K ln(C0/C)
For an isothermal second order aqueous phase reaction, A B, the ratio of the time required for 90% conversion to the time required for 45% conversion is
- 2
- 4
- 11
- 22
11
A chemical reaction is of zero order, when the reaction rate is (where, CA = concentration of reactant)
- ∝ CA.
- ∝ 1/CA.
- independent of temperature.
- none of these.
none of these.
Second order consecutive irreversible reactions A –(k1)> B–(k2)> C were carried out in a constant volume isothermal batch reactor with different initial feed compositions. Reactor temperature was same in all the cases. In experiments where the ratio of concentration of B to that of A in the initial feed was less than 0.5, the concentration of B increased first, reached a maximum and then declined with time. However, for all experiments where this concentration ratio was 0.5 or above, concentration of B decreased monotonically with time right from the beginning. What is the ratio of the two rate constants (k1/k2)?
- 1/4
- 1/2
- 2
- 4
1/4
Pick out the wrong statement.
- Catalytic activity of enzyme catalysed reactions which is affected by temperature, pH value & chemical agents, is maximum at a temperature of about 45°C.
- Most of the enzyme catalysed reactions involve at least two substrates.
- Enzymes help in increasing the activation energy of the reaction.
- Equilibrium concentrations in enzyme catalysed reactions can be calculated by using the thermodynamic properties of substrates & products.
Enzymes help in increasing the activation energy of the reaction.
There is no correspondence between stoichiometry and the rate equation in case of a/an __________ reaction.
- elementary
- multiple
- autocatalytic
- non-elementary
non-elementary
A spherical porous catalyst particle of radius R is subjected to reactant A which reacts to form B by a zero order surface reaction A → B. Film mass transfer resistance is negligible and pore diffusion of A is rate controlling. The effectiveness factor of the catalyst is reported as 7/8. Which of the following statement is true?
- Inner catalyst core of radius R/8 does not participate in reaction.
- Inner catalyst core of radius R/2 does not participate in reaction.
- Inner catalyst core of radius 7R/8 does not participate in reaction.
- Effectiveness factor for a zero order reaction can not be 7/8 as it must always be 1.
Inner catalyst core of radius R/8 does not participate in reaction.
Which of the following is used for calcination of limestone and dolomite in industrial practice ?
- Fluidised bed reactor
- Moving bed reactor
- Fixed bed reactor
- None of these
Moving bed reactor
An imbalanced chemical reaction equation is against the law of
- multiple proportion
- conservation of mass
- constant proportion
- none of these
conservation of mass
For the chemical reaction P → Q, it is found that the rate of reaction doubles as the concentration of ‘P’ is doubled. If the reaction rate is proportional to Cp^n, then what is the value of ‘n’ for this chemical reaction ?
- 1
- 2
- 3
- 0
1
Which of the following is a characteristic of an ideal plug flow reactor ?
- Axial dispersion
- Flat velocity profile
- Uniform mixing
- None of these
Flat velocity profile
Velocity of a reaction depends upon the
- nature of the reactants.
- concentration of the reactants.
- temperature at which the reaction is carried.
- all (a), (b) and (c).
all (a), (b) and (c).
Threshold energy in a reaction is equal to the
- activation energy
- normal energy of reactants
- sum of (a) & (b)
- neither (a) nor (b)
sum of (a) & (b)
An isothermal aqueous phase reversible reaction, P ⇌ R, is to be carried out in a mixed flow reactor. The reaction rate in k.mole/m^3 .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
- 0.80
- 1.33
- 1.60
- 2.67
1.60
