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

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
by

1 Answer

Answer :

(B) Porosity is of less importance
by

Related questions

Pick out the correct statement. (A) A lower temperature favours the reaction of lower activation energy (B) The dispersion number for a reactor/vessel is uL/D (C) The rate controlling step in a reaction involving many steps is the fastest step (D) Pore volume and porosity of a catalyst is measured by Brunauer￾Emmett-Teller (BET) technique

Description : Pick out the correct statement. (A) A lower temperature favours the reaction of lower activation energy (B) The dispersion number for a reactor/vessel is uL/D (C) The rate controlling step in ... step (D) Pore volume and porosity of a catalyst is measured by Brunauer￾Emmett-Teller (BET) technique

Last Answer : (A) A lower temperature favours the reaction of lower activation energy

Which one is the rate controlling step in a solid-gas non-catalytic reaction occurring at very high temperature? (A) Pore diffusion (B) Film diffusion (C) Ash layer diffusion (D) Chemical reaction

Description : Which one is the rate controlling step in a solid-gas non-catalytic reaction occurring at very high temperature? (A) Pore diffusion (B) Film diffusion (C) Ash layer diffusion (D) Chemical reaction

Last Answer : (B) Film diffusion

If a solid-gas non-catalytic reaction occurs at very high temperature, the rate controlling step is the __________ diffusion. (A) Film (B) Ash layer (C) Pore (D) None of these

Description : If a solid-gas non-catalytic reaction occurs at very high temperature, the rate controlling step is the __________ diffusion. (A) Film (B) Ash layer (C) Pore (D) None of these

Last Answer : (A) Film

In solid catalysed reactions the diffusional effects are more likely to affect the overall rate of reaction for (A) Fast reactions in catalyst of small pore diameter (B) Fast reaction in catalyst of large pore diameter (C) Slow reactions in catalyst of small pore diameter (D) Slow reactions in catalyst of large pore diameter

Description : In solid catalysed reactions the diffusional effects are more likely to affect the overall rate of reaction for (A) Fast reactions in catalyst of small pore diameter (B) Fast reaction in catalyst ... reactions in catalyst of small pore diameter (D) Slow reactions in catalyst of large pore diameter

Last Answer : (C) Slow reactions in catalyst of small pore diameter

What is the Thiele modulus of the solid catalysed first order reaction as shown in the bellow figure, if the pore diffusion offers negligible resistance to reaction? (A) < 5 (B) < 0.5(C) > 1 (D) 5

Description : What is the Thiele modulus of the solid catalysed first order reaction as shown in the bellow figure, if the pore diffusion offers negligible resistance to reaction? (A) < 5 (B) < 0.5 (C) > 1 (D) 5

Last Answer : (B) < 0.5

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)

Description : 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)

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

Helium-mercury method is used for the measurement of the __________ of the catalyst. (A) Surface area (B) Porosity (C) Pore volume (D) Both (B) & (C)

Description : Helium-mercury method is used for the measurement of the __________ of the catalyst. (A) Surface area (B) Porosity (C) Pore volume (D) Both (B) & (C)

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

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

Description : 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 ... (except the first one) is involved in each of the evaporation process (D) None of these

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

Helium-mercury method can be used to determine the __________ of the catalyst particle. (A) Pore volume (B) Solid density (C) Porosity (D) All (A), (B), & (C)

Description : Helium-mercury method can be used to determine the __________ of the catalyst particle. (A) Pore volume (B) Solid density (C) Porosity (D) All (A), (B), & (C)

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

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

Description : 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

Last Answer : (A) Specific surface of a porous catalyst

Pick out the wrong statement. (A) Exit age description function (E) and internal age distribution function (I) are related as, E = -(dI/dθ) (B) Chemisorption studies are useful in the determination of catalyst surface area and pore size distribution (C) A higher temperature favours the reaction of higher activation energy (D) A catalyst increases the potential energy barrier over which the reactants must pass to form products

Description : Pick out the wrong statement. (A) Exit age description function (E) and internal age distribution function (I) are related as, E = -(dI/dθ) (B) Chemisorption studies are useful in the ... energy (D) A catalyst increases the potential energy barrier over which the reactants must pass to form products

Last Answer : (D) A catalyst increases the potential energy barrier over which the reactants must pass to form products

Which of the following resistances is not involved in a gas phase catalytic (gas-solid) reaction?(A) Ash resistance (B) Gas film and pore surface diffusion resistances for reactants (C) Surface phenomenon resistance (D) Gas film and pore surface diffusion resistances for products

Description : Which of the following resistances is not involved in a gas phase catalytic (gas-solid) reaction? (A) Ash resistance (B) Gas film and pore surface diffusion resistances for reactants (C) Surface phenomenon resistance (D) Gas film and pore surface diffusion resistances for products

Last Answer : (A) Ash resistance

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)

. 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)

Description : . 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)

Last Answer : (C) Surface area

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

Description : 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

Last Answer : (A) Pore diffusion

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

__________ is the controlling step in a highly temperature sensitive fluid-solid non-catalytic reaction. (A) Gas film diffusion (B) Ash diffusion (C) Chemical reaction (D) None of these

Description : __________ is the controlling step in a highly temperature sensitive fluid-solid non-catalytic reaction. (A) Gas film diffusion (B) Ash diffusion (C) Chemical reaction (D) None of these

Last Answer : (C) Chemical reaction

For a solid catalysed chemical reaction, the effectiveness of solid catalyst depends upon the __________ adsorption. (A) Physical (B) Chemical (C) Both (A) and (B) (D) Neither (A) nor (B)

Description : For a solid catalysed chemical reaction, the effectiveness of solid catalyst depends upon the __________ adsorption. (A) Physical (B) Chemical (C) Both (A) and (B) (D) Neither (A) nor (B)

Last Answer : (B) Chemical

The effectiveness factor for large value of Thiele modulus [L√(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). (A) L √(K/D1 ) (B) 1/[L√(K/D1 )] (C) 1 (D) ∞

Description : The effectiveness factor for large value of Thiele modulus [L√(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). (A) L √(K/D1 ) (B) 1/[L√(K/D1 )] (C) 1 (D) ∞

Last Answer : (B) 1/[L√(K/D1 )]

If Thiele modulus is __________, then the pore diffusion resistance in a catalyst may be considered as negligible. (A) 0 (B) ∞ (C) < 0.5 (D) > 0.5

Description : If Thiele modulus is __________, then the pore diffusion resistance in a catalyst may be considered as negligible. (A) 0 (B) ∞ (C) < 0.5 (D) > 0.5

Last Answer : (C) < 0.5

Bulk diffusion in catalyst pore __________ with increase in pressure. (A) Increases (B) Decreases (C) Remains unchanged (D) Increases exponentially

Description : Bulk diffusion in catalyst pore __________ with increase in pressure. (A) Increases (B) Decreases (C) Remains unchanged (D) Increases exponentially

Last Answer : (B) Decreases

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

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

Last Answer : (A) Diffusion within the pellet

Promoter is added to the catalyst to improve its (A) Porosity (B) Sensitivity (C) Surface area (D) None of these

Description : Promoter is added to the catalyst to improve its (A) Porosity (B) Sensitivity (C) Surface area (D) None of these

Last Answer : (B) Sensitivity

If the pore diffusion controls in a catalytic reaction, the apparent activation energy Ea is equal to (A) The intrinsic activation energy E (B) (E + ED) where ED is activation due to diffusion (C) (E + ED)/2 (D) ED/2

Description : If the pore diffusion controls in a catalytic reaction, the apparent activation energy Ea is equal to (A) The intrinsic activation energy E (B) (E + ED) where ED is activation due to diffusion (C) (E + ED)/2 (D) ED/2

Last Answer : (D) ED/2

Pick out the correct statement. (A) Reactions with high activation energies are very temperature sensitive (B) Chemical equilibrium is a static state (C) A photochemical reaction is catalysed by light (D) A chemical reaction occurs when the energy of the reacting molecule is less than the activation energy of the reaction

Description : Pick out the correct statement. (A) Reactions with high activation energies are very temperature sensitive (B) Chemical equilibrium is a static state (C) A photochemical reaction is catalysed by ... occurs when the energy of the reacting molecule is less than the activation energy of the reaction

Last Answer : (A) Reactions with high activation energies are very temperature sensitive (B) Chemical equilibrium is a static state

For a heterogeneous catalytic reaction, A + B → C, with equimole feed of A and B, the initial rate - rA0 is invariant with total pressure. The rate controlling step is (A) Surface Kc /(1 + TS ) reaction between absorbed A and B in the gas phase (B) Surface reaction between absorbed A and absorbed B (C) Surface reaction between A in the gas phase and absorbed B(D) Desorption of C

Description : For a heterogeneous catalytic reaction, A + B → C, with equimole feed of A and B, the initial rate - rA0 is invariant with total pressure. The rate controlling step is (A) Surface Kc /(1 + TS ) ... A and absorbed B (C) Surface reaction between A in the gas phase and absorbed B (D) Desorption of C

Last Answer : (D) Desorption of C

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

Description : 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 ... to (B) Independent of (C) Inversely proportional to (D) Proportional to the square o

Last Answer : (A) Proportional to

For high conversion in a highly exothermic solid catalysed reaction, use a __________ bed reactor. (A) Fixed (B) Fluidised bed reactor followed by a fixed (C) Fixed bed reactor followed by a fluidised (D) Fluidised

Description : For high conversion in a highly exothermic solid catalysed reaction, use a __________ bed reactor. (A) Fixed (B) Fluidised bed reactor followed by a fixed (C) Fixed bed reactor followed by a fluidised (D) Fluidised

Last Answer : (B) Fluidised bed reactor followed by a fixed

Kinetics of a solid catalysed reaction can best be studied in a __________ reactor. (A) Batch (B) Plug-flow (C) Mixed (D) None of these

Description : Kinetics of a solid catalysed reaction can best be studied in a __________ reactor. (A) Batch (B) Plug-flow (C) Mixed (D) None of these

Last Answer : (C) Mixed

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

Description : 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 ( ... + kg )/2 (C) ke ff = (kkg ) 1/2 (D) 1/ke ff = 1/k + 1/kg

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

The Knudsen diffusivity is dependent on the (A) Molecular velocity only (B) Pore radius of the catalyst only (C) Molecular mean free path only (D) Molecular velocity and pore radius of the catalyst

Description : The Knudsen diffusivity is dependent on the (A) Molecular velocity only (B) Pore radius of the catalyst only (C) Molecular mean free path only (D) Molecular velocity and pore radius of the catalyst

Last Answer : (D) Molecular velocity and pore radius of the catalyst

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 (A) Pressure (B) Temperature (C) Both (A) & (B) (D) Neither (A) nor (B)

Description : 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 (A) Pressure (B) Temperature (C) Both (A) & (B) (D) Neither (A) nor (B)

Last Answer : (B) Temperature

For the non catalytic reaction of particles with surrounding fluid, the same needed to achieve the same fractional conversion for particles of different unchanging sizes is proportional to the particle diameter, when the __________ is the controlling resistance. (A) Film diffusion (B) Diffusion through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Description : For the non catalytic reaction of particles with surrounding fluid, the same needed to achieve the same fractional conversion for particles of different unchanging sizes is proportional to the particle diameter, when the ... through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Last Answer : (C) Chemical reaction

For the non-catalytic reaction of particles with surrounding fluid, the time needed to achieve the same fractional conversion for particles of different but unchanging sizes is proportional to the square of particle diameter, when the __________ is the controlling resistance. (A) Film diffusion (B) Diffusion through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Description : For the non-catalytic reaction of particles with surrounding fluid, the time needed to achieve the same fractional conversion for particles of different but unchanging sizes is proportional to the square of particle diameter, ... through ash layer (C) Chemical reaction (D) Either (A), (B) or (C)

Last Answer : (B) Diffusion through ash layer

A catalyst loses its activity due to (A) Loss in surface area of the active component (B) Agglomeration of metal particles caused by thermal sintering of the solid surface (C) Covering of the catalytic active sites by a foreign substance (D) All (A), (B) and (C)

Description : A catalyst loses its activity due to (A) Loss in surface area of the active component (B) Agglomeration of metal particles caused by thermal sintering of the solid surface (C) Covering of the catalytic active sites by a foreign substance (D) All (A), (B) and (C)

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

Pick out the correct statement. (A) Higher hold up of the solid in the rotary dryer results in better exposure of the solids to the gas (B) The 'Hatta number' is important in problems involving gas absorption without chemical reaction (C) For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal counter-diffusion (D) Total reflux in case of distillation operation requires infinite number of plates for a binary system separation

Description : Pick out the correct statement. (A) Higher hold up of the solid in the rotary dryer results in better exposure of the solids to the gas (B) The 'Hatta number' is ... reflux in case of distillation operation requires infinite number of plates for a binary system separation

Last Answer : (C) For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal counter-diffusion

Bed pressure drop in an air fluidised bed of catalyst particles (ρp = 200 kg/m3, Dp = 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is (A) 90 (B) 60 (C) 45 (D) 30

Description : Bed pressure drop in an air fluidised bed of catalyst particles (ρp = 200 kg/m3, Dp = 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is (A) 90 (B) 60 (C) 45 (D) 30

Last Answer : (B) 60

Finely divided catalyst has greater surface area and has greater catalytic activity than the compact solid. If a total surface area of 6291456 `cm^(2)

Description : Finely divided catalyst has greater surface area and has greater catalytic activity than the compact solid. If a total surface area of 6291456 `cm^(2)

Last Answer : Finely divided catalyst has greater surface area and has greater catalytic activity than the compact solid. If a total ... B. `80` C. `20` D. `22`

The neutral stress in a soil mass is (A) Force per neutral area (B) Force per effective area (C) Stress taken up by the pore water (D) Stress taken up by solid particles

Description : The neutral stress in a soil mass is (A) Force per neutral area (B) Force per effective area (C) Stress taken up by the pore water (D) Stress taken up by solid particles

Last Answer : Answer: Option C

The effect of the temperature rising above 100ºC on heat-cured denture-base acrylic resins is: A. Produces porosity on the external portion of the resin. B. Produces porosity on the internal portion of the resin. C. Produces porosity on the surface of the resin. D. Prevents porosity on the interior of the resin

Description : The effect of the temperature rising above 100ºC on heat-cured denture-base acrylic resins is: A. Produces porosity on the external portion of the resin. B. Produces porosity on the internal portion ... porosity on the surface of the resin. D. Prevents porosity on the interior of the resin

Last Answer : B. Produces porosity on the internal portion of the resin.

Which of the following is not a chemical step in a fluid solid catalytic reaction? (A) Surface chemical reaction (B) Adsorption (C) Desorption (D) None of these

Description : Which of the following is not a chemical step in a fluid solid catalytic reaction? (A) Surface chemical reaction (B) Adsorption (C) Desorption (D) None of these

Last Answer : (D) None of these

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

Description : 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 ... with the reactant (D) The surface of the catalyst does not play an important role during reaction

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

Catalyst carriers (A) Have very high selectivity (B) Increase the activity of a catalyst (C) Provide large surface area with a small amount of active material (D) Inhibit catalyst poisoning

Description : Catalyst carriers (A) Have very high selectivity (B) Increase the activity of a catalyst (C) Provide large surface area with a small amount of active material (D) Inhibit catalyst poisoning

Last Answer : (C) Provide large surface area with a small amount of active material

(A) Measures the catalyst surface area directly (B) Operates at very high pressure (C) Is made entirely of stainless steel (D) None of these

Description : BET apparatus (A) Measures the catalyst surface area directly (B) Operates at very high pressure (C) Is made entirely of stainless steel (D) None of these

Last Answer : (D) None of these

Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface? (A) Liquid density (B) Liquid viscosity (C) Hot surface temperature (D) Interfacial tension

Description : Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface? (A) Liquid density (B) Liquid viscosity (C) Hot surface temperature (D) Interfacial tension

Last Answer : (D) Interfacial tension

Which is the controlling factor for a drum drier? (A) Diffusion (B) Heat transfer

Description : Which is the controlling factor for a drum drier? (A) Diffusion (B) Heat transfer

Last Answer : (B) Heat transfer

The rate limiting step in catecholamine synthesis is catalysed by (A) Phenylalanine hydroxylase (B) Tyrosine hydroxylase (C) Dopa decarboxylase (D) Phenylethanolamine N-methyl transferase

Description : The rate limiting step in catecholamine synthesis is catalysed by (A) Phenylalanine hydroxylase (B) Tyrosine hydroxylase (C) Dopa decarboxylase (D) Phenylethanolamine N-methyl transferase

Last Answer : Answer : B

The initial step of the citric acid cycle is (A) Conversion of pyruvate to acetyl-CoA (B) Condensation of acetyl-CoA with oxaloacetate (C) Conversion of citrate to isocitrate (D) Formation of α -ketoglutarate catalysed by isocitrate dehydrogenase

Description : The initial step of the citric acid cycle is (A) Conversion of pyruvate to acetyl-CoA (B) Condensation of acetyl-CoA with oxaloacetate (C) Conversion of citrate to isocitrate (D) Formation of α -ketoglutarate catalysed by isocitrate dehydrogenase

Last Answer : Answer : B

With increase in porosity, the thermal conductivity of a solid substance (A) Increases (B) Decreases (C) Remains unchanged (D) May increase or decrease; depends on the solid

Description : With increase in porosity, the thermal conductivity of a solid substance (A) Increases (B) Decreases (C) Remains unchanged (D) May increase or decrease; depends on the solid

Last Answer : (B) Decreases