chemical engineering MCQs – Page 143

Practise multiple-choice questions from chemical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

chemical engineering Mcqs
2841. 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_______________________?
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A. d(VCA)/dt = F (CAF CA) kCA2V

B. d(VCA)/dt = -F (CAF CA) kCA2V

C. d(VCA)/dt = FCAF kCA2V

D. d(VCA)/dt = -FCA kCA2V

2842. For all positive reaction orders for a particular duty ?
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A. Reactor size is independent of the type of flow

B. Mixed reactor is always larger than the plug-flow reactor

C. Density variation during reaction affects design

D. Ratio of the volume of the mixed reactor to that of the plug-flow reactor decreases with order

2843. Promoter is added to the catalyst to improve its____________________?
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A. Porosity

B. Sensitivity

C. Surface area

D. None of these

2844. The extent of a reaction is ___________________?
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A. Dimensionless

B. All of the above

C. Depends on the stoichiometric co-efficient

D. Different for reactants and products

2845. In a chemical reaction, represented by as shown in the bellow figure, it is observed that the (i) Rate of reaction increases by a factor of 4 on doubling the concentration of the reactant. (ii) Rate of reaction increases by a factor of 9 on trebling the concentration of the reactant. Then the rate of the reaction is proportional to(where, CA = concentration of the reactant)_____________________?
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A. CA4

B. CA2

C. CA

D. CA3

2846. Half life period of a chemical reaction is_________________?
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A. None of these

B. Half of the residence time of a reaction

C. Half of the space time of a reaction

D. The time required to reduce the concentration of the reacting substance to half its initial value
2847. The minimum energy required to allow a chemical reaction to proceed is termed as the threshold energy . Chemical reactions with low activation energy are ________________?
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A. Mostly irreversible

B. Highly temperature sensitive

C. Insensitive to temperature changes

D. Always irreversible

2848. Which of the following is the most suitable for very high pressure gas phase reaction ?
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A. Tubular flow reactor

B. Stirred tank reactor

C. Batch reactor

D. Fluidised bed reactor

2849. A pulse tracer is introduced in an ideal CSTR (with a mean residence time I) at time, t = 0. The time taken for the exit concentration of the tracer to reach half of its initial value will be__________________?
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A. 0.693?

B. 2?

C. 0.5?

D. ?/0.693

2850. A reaction which is catalysed by an acid is also catalysed by any substance, which has a tendency to _________________?
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A. None of these

B. Lose a proton

C. Gain a proton

D. Lose an electron

2851. Organic catalysts differ from the inorganic catalyst in the sense that the former is________________?
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A. Proteinous in nature

B. Active at very high temperature only

C. Active at cryogenic temperatures only

D. Prohibitively costly

2852. A batch reactor suffers from following disadvantage ?
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A. All A., B. and C.

B. High labour and handling cost

C. Poor product quality control

D. High shutdown time requirement for emptying, cleaning and refilling

2853. Limiting reactant in a chemical reaction decides the____________________?
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A. Reaction speed

B. Rate constant

C. Equilibrium constant

D. Conversion
2854. Kinetics of a catalytic reaction can be best studied on a/an ______________ reactor?
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A. Integral (plug flow)

B. Differential (flow)

C. Mixed

D. Either A., B. and C.
2855. Vegetable oils are hydrogenated in a _______________ reactor?
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A. Plug flow

B. Homogeneous catalytic

C. None of these

D. Slurry
2856. The space time is equivalent to the holding time in a steady state mixed reactor for_____________________?
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A. Non-isothermal gas reaction

B. Gas reactions with changing number of moles

C. Constant fluid density systems

D. Variable fluid density systems

2857. In a CSTR _______________ varies with time ?
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A. Reaction rate

B. Concentration

C. Both A. & B.

D. Neither A. nor B.
2858. If pore diffusion is the controlling step in a solid catalysed reaction, the catalyst___________________?
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A. Porosity is of less importance

B. None of these

C. Porosity is very important

D. Internal surface area is utilised efficiently

2859. Oil is hydrogenated using nickel catalyst in a __________________ reactor?
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A. Batch

B. Slurry

C. Fluidised bed

D. Fixed bed

2860. For a first order isothermal chemical reaction in a porous catalyst, the effectiveness factor is 0.3. The effectiveness factor will increase if the____________________?
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A. Catalyst size is reduced or the catalyst diffusivity is increased

B. Catalyst size is reduced or the catalyst diffusivity is reduced

C. Catalyst size is increased or the catalyst diffusivity is reduced

D. Catalyst size is increased or the catalyst diffusivity is increased