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 (A) Diffusion within the pellet (B) Reaction (C) External mass transfer (D) None of the above

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
(A) Diffusion within the pellet
(B) Reaction
(C) External mass transfer
(D) None of the above
by

1 Answer

Answer :

(A) Diffusion within the pellet
by

Related questions

Which of the following factors control the deactivation of a porous catalyst pellet? (A) Decay reactions (B) Pore diffusion (C) Form of surface attack by poison (D) All (A), (B) and (C)

Description : Which of the following factors control the deactivation of a porous catalyst pellet? (A) Decay reactions (B) Pore diffusion (C) Form of surface attack by poison (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

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) (A) tan hT/T (B) tan T/T(C) tan hT/tan T(D) None of these

Description : 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) (A) tan hT/T (B) tan T/T (C) tan hT/tan T (D) None of these

Last Answer : (A) tan hT/T

For a first order isothermal chemical reaction in a porous catalyst, the effectiveness factor is 0.3. The effectiveness factor will increase if the (A) Catalyst size is reduced or the catalyst diffusivity is reduced (B) Catalyst size is reduced or the catalyst diffusivity is increased (C) Catalyst size is increased or the catalyst diffusivity is reduced(D) Catalyst size is increased or the catalyst diffusivity is increased

Description : For a first order isothermal chemical reaction in a porous catalyst, the effectiveness factor is 0.3. The effectiveness factor will increase if the (A) Catalyst size is reduced or the ... the catalyst diffusivity is reduced (D) Catalyst size is increased or the catalyst diffusivity is increased

Last Answer : (B) Catalyst size is reduced or the catalyst diffusivity is increased

Effectiveness factor of a catalyst pellet is a measure of the __________ resistance. (A) Pore diffusion (B) Gas film (C) Chemical reaction (D) None of these

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Last Answer : (A) Pore diffusion

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 (ke ff) is given by (A) ke ff = k + kg (B) ke ff = (k+ kg )/2 (C) ke ff = (kkg ) 1/2 (D) 1/ke ff = 1/k + 1/kg

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Last Answer : (D) 1/ke ff = 1/k + 1/kg

Pick out the wrong statement. (A) 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 (B) Transition state theory approaches the problem of calculating reaction rates by concentrating on the idea of activated complexes (C) According to the penetration theory, the mass transfer co-efficient decreases, if the exposure time of an eddy to the solute decreases (D) If the rate of an irreversible reaction, A + B → 2C is k.CA .CB , then the reaction is always elementary

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Overall rate of reaction in a heterogeneous 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 doesnot entail a chain mechanism.(A) Proportional to(B) Independent of(C) Inversely proportional to(D) Proportional to the square o

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Last Answer : (A) Proportional to

For a first order chemical reaction in a porous catalyst, the Thiele modulus is 10. The effectiveness factor is approximately equal to (A) 0 (B) 1 (C) 0.1 (D) 0.5

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Last Answer : (C) 0.1

For preparation of porous bearings by powder metallurgy, preferred particle shape is (A) Spherical (B) Nodular (C) Irregular (D) No preferred shape

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Last Answer : (A) Spherical

. 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: (A) 2 (B) 4 (C) 11 (D) 22

Description : . 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: (A) 2 (B) 4 (C) 11 (D) 22

Last Answer : (C) 11

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 (A) 0 (B) 1 (C) 1.5 (D) 2

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Last Answer : (A) 0

Brunauer, 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? (A) Langmuir's assumption applies to every adsorbed layer (B) There is no dynamic equilibrium between successive layer (C) 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 (D) None of these

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Last Answer : (B) There is no dynamic equilibrium between successive layer

A second order liquid phase reaction, A → B, is carried out in a mixed flow reactor operated in semi batch mode (no exit stream). The reactant A at concentration CAF is fed to the reactor at a volumetric flow rate of F. The volume of the reacting mixture is V and the density of the liquid mixture is constant. The mass balance for A is (A) d(VCA )/dt = -F (CAF - CA ) - kCA 2V (B) d(VCA )/dt = F (CAF - CA ) - kCA 2V (C) d(VCA )/dt = -FCA - kCA 2V (D) d(VCA )/dt = FCAF - kCA 2V

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Last Answer : (D) d(VCA )/dt = FCAF - kCA 2V

If pore diffusion is the controlling step in a solid catalysed reaction, the catalyst (A) Porosity is very important (B) Porosity is of less importance (C) Internal surface area is utilised efficiently (D) None of these

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BET apparatus is used to determine the (A) Specific surface of a porous catalyst (B) Pore size distribution (C) Pore diameter (D) Porosity of the catalyst bed

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. B.E.T. method can be used to determine the __________ of a porous catalyst. (A) Solid density (B) Pore volume (C) Surface area (D) All (A), (B) and (C)

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When an isolated thermodynamic system executes a process, (A) Work is done (B) Heat transfer takes place (C) Mass flow occurs across the boundary of the system (D) No chemical reaction takes place within the system

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The fractional volume change of the system for the isothermal gas phase reaction, A → 3B, between no conversion and complete conversion is (A) 0.5 (B) 1 (C) 2 (D) 3

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Last Answer : (C) 2

The fractional volume change between no conversion and complete conversion, for the isothermal gas phase reaction, 2A → R, is (A) 0.5 (B) -0.5 (C) 1 (D) 1.5

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Last Answer : (B) -0.5

A pure drug is administered as a sphere and as a cube. The amount of drug is the same in the two tablets. Assuming that the shape and size do not influence the mass transfer, the ratio of rate of dissolution in water at t = 0for the cubic to spherical tablet is: (A) 0.54 (B) 1.04 (C) 1.24 (D) 1.94

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Last Answer : (C) 1.24

. A first order irreversible reaction, A → B is carried out separately in a constant volume as well as in a variable volume reactor for a particular period. It signifies that __________ in the two reactors. (A) Both conversion as well as concentration are same (B) Conversion in both will be the same but concentrations will be different (C) Both the conversion as well as concentrations will be different (D) None of these

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Last Answer : (B) Conversion in both will be the same but concentrations will be different

The concentration of A in a first order reaction, A → B, decreases (A) Linearly with time (B) Exponentially with time (C) Very abruptly towards the end of the reaction (D) Logarithmically with time

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The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, Kp= M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.) (A) Kc = Kp = Km (B) Kc = Kp /RT = Km . RT/P (C) Kc = Kp . RT = Km . RT/p (D) None of these

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Last Answer : (C) Kc = Kp . RT = Km . RT/p

Effective diffusivity (DE) in a catalyst pellet is related to molecular diffusivity (DN) and Knudsen diffusivity (DK) as (A) DE = DM + DK (B) 1/DE = 1/DN + DK (C) DE = DM . DE (D) DE = DN/DE

Description : Effective diffusivity (DE) in a catalyst pellet is related to molecular diffusivity (DN) and Knudsen diffusivity (DK) as (A) DE = DM + DK (B) 1/DE = 1/DN + DK (C) DE = DM . DE (D) DE = DN/DE

Last Answer : (B) 1/DE = 1/DN + DK

Temperature during hydrogenation of oil should not be more than 200°C, otherwise it will result in (A) Pyrolysis of oil(B) Sintering of porous catalyst(C) Hydrogen embrittlement(D) All (A), (B) and (C)

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For a heterogeneous catalytic reaction (A) Free energy of activation is lowered in the presence of catalyst, which remains unchanged at the end of reaction (B) A relatively small amount of catalyst can cause the conversion of large amount of reactants which does not mean that catalyst concentration is important (C) The catalyst does not form an intermediate complex with the reactant (D) The surface of the catalyst does not play an important role during reaction

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Last Answer : (A) Free energy of activation is lowered in the presence of catalyst, which remains unchanged at the end of reaction

T.V. transmission cannot cover a very large area because _____ A. The strength of T.V. waves is very limited B. Picture cannot be transmitted clearly after a specific distance C. The shape of the earth is spherical D. The air is not a good conductor of light and sound/waves

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Last Answer : ANSWER: C

Range of Television Broadcasting is confined to a limited distance because (a) Long waves are used (b) Short waves are absorbed by atmosphere (c) Energy of the waves is dissipated (d) Earth is spherical in shape

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Last Answer : Ans:(d)

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Last Answer : C. the shape of the earth is spherical (Answer)

Catalyst used in the manufacture of sulphuric acid by chamber & contact processes are respectively (A) V2O5 & Cr2O3 . (B) Oxides of nitrogen & Cr2O3 (C) V2O5 on a porous carrier & oxides of nitrogen (D) Oxides of nitrogen & V2O5 on a porous carrier

Description : Catalyst used in the manufacture of sulphuric acid by chamber & contact processes are respectively (A) V2O5 & Cr2O3 . (B) Oxides of nitrogen & Cr2O3 (C) V2O5 on a porous carrier & oxides of nitrogen (D) Oxides of nitrogen & V2O5 on a porous carrier

Last Answer : (D) Oxides of nitrogen & V2O5 on a porous carrier

Pick out the wrong statement. (A) The binary diffusivity in liquids is of the order of 10 -5 cm2 /sec (B) Molecular diffusion in solid is much faster than that in liquids (C) Particles movement from higher concentration to lower concentration takes place in diffusion process (D) According to Poiseuille's law, the permeability decreases with increase in temperature for flow of a gas through a given capillary

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Last Answer : (B) Molecular diffusion in solid is much faster than that in liquids

Pick up the correct statement from the following: (A) According to the petrological characteristics, concrete aggregates are classified as heavy weight, normal weight and light weight (B) According to the shape of the particles, concrete aggregates are classified as rounded irregular, angular and flaky (C) According to the surface texture of the particles, the concrete aggregates are classified as glassy, smooth, granular, rough, crystalline, honey combed and porous (D) All the above

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The importance of diffusion in a catalyst are increased by (A) Large catalyst particle size (B) An active surface of the catalyst (C) Small pore diameter (D) All (A), (B) and (C)

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Last Answer : (D) All (A), (B) and (C)

Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular diffusion, if (A) Mass transfer is accompanied by reaction (B) Diffusion of A is in stagnant medium B (C) Molecular mean free path is high (D) There is equimolar counter diffusion

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Last Answer : (D) There is equimolar counter diffusion

Analogy between mass and heat transfer is not applicable in case of (A) Same velocity profile or equal eddy diffusivities (B) Thermal or pressure mass diffusion (C) Viscous heating or chemical reaction (D) Both (B) and (C)

Description : Analogy between mass and heat transfer is not applicable in case of (A) Same velocity profile or equal eddy diffusivities (B) Thermal or pressure mass diffusion (C) Viscous heating or chemical reaction (D) Both (B) and (C)

Last Answer : (D) Both (B) and (C)

For the chemical reaction X → Y, it is observed that, on doubling the concentration of 'X', the reaction rate quadruples. If the reaction rate is proportional to Cx n , then what is the value of ‘n’? (A) 1/4 (B) 2 (C) 4 (D) 16

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Last Answer : (C) 4

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? (A) 0 (B) 1 (C) 2 (D) 3

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Last Answer : (B) 1

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)) (A) 400 (B) 500 (C) 600 (D) 1000

Description : 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 ... /kmole. K (may be assumed to be independent of temperature)) (A) 400 (B) 500 (C) 600 (D) 1000

Last Answer : (C) 600

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 (A) Higher in P.F. reactor (B) Higher in CSTR (C) Same in both the reactors (D) Data insufficient; can't be predicted

Description : 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 (A) Higher in P.F. reactor (B) Higher in CSTR (C) Same in both the reactors (D) Data insufficient; can't be predicted

Last Answer : (A) Higher in P.F. reactor

The irreversible reaction, X → Y, is the special case of the reversible reaction, X ⇌ Y, in which the (A) Equilibrium constant is infinite (B) Fractional conversion of 'A' at equilibrium is unity (C) Concentration of 'A' at equilibrium is zero (D) All (A), (B) and (C)

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Last Answer : (D) All (A), (B) and (C)

What is the value of 'n' if the reaction rate of the chemical reaction A → B, is proportional to CA n and it is found that the reaction rate triples, when the concentration of 'A' is increased 9 times? (A) 1/2 (B) 1/3 (C) 1/9 (D) 3

Description : What is the value of 'n' if the reaction rate of the chemical reaction A → B, is proportional to CA n and it is found that the reaction rate triples, when the concentration of 'A' is increased 9 times? (A) 1/2 (B) 1/3 (C) 1/9 (D) 3

Last Answer : (A) 1/2

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 CA n , then what is the value of n for this reaction? (A) 0 (B) 0.5 (C) 1 (D) 2

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Last Answer : (C) 1

The value of 'n' for a chemical reaction A → B, whose reaction rate is → CA n , will be __________ if the rate of the reaction increases by a factor of 8, when the concentration of is doubled. (A) 0 (B) 1 (C) 2 (D) 3

Description : The value of 'n' for a chemical reaction A → B, whose reaction rate is → CA n , will be __________ if the rate of the reaction increases by a factor of 8, when the concentration of is doubled. (A) 0 (B) 1 (C) 2 (D) 3

Last Answer : (D) 3

Centre of pressure of a plane surface of arbitrary shape immersed vertically in a static mass of fluid(A) Lies above the centroid of the plane surface(B) Is independent of the specific weight of the fluid(C) Is different for different fluids(D) Is at the centroid of the plane surface

Description : Centre of pressure of a plane surface of arbitrary shape immersed vertically in a static mass of fluid (A) Lies above the centroid of the plane surface (B) Is independent of the specific weight of the fluid (C) Is different for different fluids (D) Is at the centroid of the plane surface

Last Answer : (B) Is independent of the specific weight of the fluid

Molecular diffusion is caused by the (A) Transfer of molecules from low concentration to high concentration region (B) Thermal energy of the molecules (C) Activation energy of the molecules (D) Potential energy of the molecules

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Last Answer : (B) Thermal energy of the molecules

The fluid property which matters for falling rain drops to acquire spherical shape is its (A) Pressure (B) Height of descend (C) Viscosity (D) Surface tension

Description : The fluid property which matters for falling rain drops to acquire spherical shape is its (A) Pressure (B) Height of descend (C) Viscosity (D) Surface tension

Last Answer : (D) Surface tension

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Description : Surface tension of a liquid (A) Is due to intermolecular forces of cohesion (B) Decreases with rise in temperature (C) Is responsible for the spherical shape of an isolated liquid drop (D) All (A), (B) & (C)

Last Answer : (D) All (A), (B) & (C)