chemical engineering MCQs – Page 150

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 Review each marked answer and report any item that may be outdated or unclear.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

2981. The reaction A ? B is conducted in an adiabatic plug flow reactor (PFR). Pure A at a concentration of 2 kmol/m3is 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)) ?
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A. 1000

B. 400

C. 600

D. 500

2982. BET apparatus is used to determine the ___________________?
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A. Specific surface of a porous catalyst

B. Pore diameter

C. Porosity of the catalyst bed

D. Pore size distribution

2983. 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______________________?
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A. Desorption of C

B. Surface reaction between A in the gas phase and absorbed B

C. Surface reaction between absorbed A and absorbed B

D. Surface Kc/(1 + TS) reaction between absorbed A and B in the gas phase

2984. The optimum performance for reactors operating in parallel is obtained when the feed stream is distributed in such a way, that the_________________?
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A. None of these

B. Space time for parallel lines is different

C. Larger reactors have more space time compared to smaller ones

D. Space time for each parallel line is same

2985. The reaction rate constants at two different temperatures T1 and T2 are related by _________________?
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A. exp (k2/k1) = (E/R) (1/T2 1/T1)

B. exp (k2/k1) = (E/R) (1/T1 1/T2)

C. ln (k2/k1) = (E/R) (1/T2 1/T1)

D. ln (k2/k1) = (E/R) (1/T1 1/T2)

2986. n number of plug flow reactors (P.F.R) in series with a total volume V gives the same conversion as one P.F.R. of volume________________?
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A. V/n

B. V

C. V.n

D. 1/V

2987. The rate of reaction does not decrease appreciably as the reaction proceeds in case of ______________ reactions?
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A. Endothermic

B. Autothermal

C. Autocatalytic

D. Exothermic

2988. A liquid phase reaction is to be carried out under isothermal conditions. The reaction rate as a function of conversion has been determined experimentally and is shown in the figure given below. What choice of reactor or combination of reactors will require the minimum overall reactor volume, if a conversion of 0.9 is desired ?
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A. PFR followed by a CSTR

B. CSTR followed by a PFR

C. CSTR followed by a PFR followed by a CSTR

D. PFR followed by a CSTR followed by a PFR

2989. 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________________?
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A. 1/keff = 1/k + 1/kg

B. keff = k + kg

C. keff = (k+ kg)/2

D. keff = (kkg)1/2

2990. The following gas phase reaction is taking place in a plug flow reactor. A stoichiometric mixture of A and B at 300 K is fed to the reactor. At 1 m along the length of the reactor, the temperature is 360 K. The pressure drop is negligible and an ideal gas behaviour can be assumed. Identify the correct expression relating the concentration of A at the inlet (CA0), concentration of A at 1m (CA) and the corresponding conversion of A (X) ?
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A. CA = 0.83 CA0 (1 X)/(1 0.33X)

B. CA = 1.2 CA0 (1 X)/(1 0.5X)

C. CA = 1.2 CA0 (1 X)/(1 0.33X)

D. CA = 0.83 CA0 (1 X)/(1 0.5X)

2991. Arrhenius equation shows the variation of ___________________ with temperature?
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A. Rate constant

B. Reaction rate

C. Energy of activation

D. Frequency factor

2992. Rate of an autocatalytic chemical reaction is a function of ___________________?
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A. All A., B. and C.

B. Pressure only

C. Composition only

D. Temperature only

2993. The fractional volume change between no conversion and complete conversion, for the isothermal gas phase reaction, 2A ? R, is___________________?
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A. 0.5

B. 1.5

C. 1

D. -0.5

2994. 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 _______________?
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A. Two

B. Three

C. One

D. Zero

2995. Calcination reaction of limestone (CaCO3 ? CaO + CO2) goes to completion in the rotary kiln, because____________________?
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A. CO2 escapes continuously

B. Of high calcination temperature

C. CaO is more stable than CaCO3

D. CaO is not dissociated

2996. A catalyst inhibitor____________________?
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A. Is added in small quantity during the catalyst manufacture itself

B. May be useful for suppressing undesirable side reactions

C. All A., B. and C.

D. Lessens its selectivity

2997. The irreversible reaction, X ? Y, is the special case of the reversible reaction, X ? Y, in which the _____________________?
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A. Fractional conversion of A at equilibrium is unity

B. Concentration of A at equilibrium is zero

C. All A., B. and C.

D. Equilibrium constant is infinite

2998. The concentration of A in a first order reaction, A ? B, decreases_____________________?
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A. Linearly with time

B. Logarithmically with time

C. Exponentially with time

D. Very abruptly towards the end of the reaction

2999. Fluidised bed reactor is characterized by____________________?
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A. Absence of continuous catalyst regeneration facility

B. Uniformity of temperature

C. Comparatively smaller equipment

D. Very small pressure drop

3000. For reactions in parallel viz A ? P (desired product) and A ? Q (unwanted product), if the order of the desired reaction is higher than that of the undesired reaction, a_________________?
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A. Batch reactor is preferred over a single CSTR for high yield

B. Tubular reactor is preferred over a single CSTR for high yield

C. Both A. and B.

D. Single CSTR is the most suitable

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