Explore topic-wise MCQs in Chemical Engineering.

This section includes 119 Mcqs, each offering curated multiple-choice questions to sharpen your Chemical Engineering knowledge and support exam preparation. Choose a topic below to get started.

1.

For a tubular reactor with space time \'τ\' and residence time \'θ\', the following statement holds good.

A. τ = θ , when the fluid density changes in the reactor
B. τ and θ are always equal.
C. τ = θ , for a non-isothermal reactor
D. τ = θ , for an isothermic tubular reactor in which the density of the process fluid is constant
Answer» E.
Discussion
2.

The first order series reaction is conducted in a batch reactor. The initial concentrations of A, B and C ( C A 0 , C B 0 , C C 0 respectively) are all non-zero. The variation of C B with reaction time will not show a maximum, if

A. k 2 C B 0 > k 1 C A 0
B. k C A 0 > k 2 . C B 0
C. C B 0 > C A 0
D. C A 0 > C B 0
Answer» B. k C A 0 > k 2 . C B 0
Discussion
3.

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.
Answer» B. reaction.
Discussion
4.

The effectiveness factor for large value of Thiele modulus ( L K / D 1 ) of a solid catalysed first order reaction is equal to (where, L = length of the reactor, cm, D 1 = diffusion co-efficient, cm 2 /second)

A. L ( K / D 1 )
B. 1/( L K / D 1 )
C. 1
D. ?
Answer» C. 1
Discussion
5.

In a chemical reaction, repesented by, , 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, C A = contentration of the reactant)

A. C A
B. C A 2
C. C A 3
D. C A 4
Answer» C. C A 3
Discussion
6.

The rate of a gas phase reaction is given by K . C A . C B . If the volume of the reaction vessel is reduced to l/4th of its initial volume, then the reaction rate compared to the original rate will be __________ times.

A. 4
B. 16
C. 8
D. 2
Answer» C. 8
Discussion
7.

Effectiveness factor ( E ) of a catalyst pellet is defined as, 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
Answer» B. tan T / T
Discussion
8.

A second order reaction of the form A + B C is called a pseudo-first order reaction, when

A. C A 0 = C B 0
B. C A 0 > C B 0
C. C B 0 > C A 0
D. C B 0 ? C B 0
Answer» E.
Discussion
9.

What is the value of ' n ' if the reaction rate of the chemical reaction A B , is proportional to C A 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
Answer» B. 1/3
Discussion
10.

For reaction, P + 2 3 R , molar rate of consumption of P is

A. double of that of Q .
B. same as that of Q .
C. half of that of Q .
D. 2/3rd of that of Q .
Answer» D. 2/3rd of that of Q .
Discussion
11.

In the hydrodealkylation of toluene to benzene, the following reactions occur: C 7 H 8 + H 2 C 6 H 6 + CH 4 2C 6 H 6 C 12 H 10 + H 2 Toluene and hydrogen are fed to a reactor in a molar ratio 1:5.80% of the toluene gets converted and the selectivity of benzene(defined as moles of benzene formed/moles of toluene converted) is 90%. The fractional conversion of hydrogen is

A. 0.16
B. 0.144
C. 0.152
D. 0.136
Answer» C. 0.152
Discussion
12.

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.
Answer» C. very abruptly towards the end of the reaction.
Discussion
13.

The conversion for a first order liquid phase reaction. A B in a CSTR is 50%. If another CSTR of the same volume is connected in series, then the % conversion at the exit of the second reactor will be

A. 60
B. 75
C. 90
D. 100
Answer» C. 90
Discussion
14.

If helium is introduced in a reactor containing O 2 , SO 2 and SO 3 at equilibrium, so that total pressure increases while volume and temperature remains constant. In this case the dissociation of SO 3 (as per Le Chatlier principle)

A. decreases
B. increases
C. remains unaltered
D. changes unpredictably.
Answer» B. increases
Discussion
15.

For a __________ order chemical reaction, , the fractional conversion of reactant ' A ' is proportional to time.

A. zero
B. first
C. second
D. third
Answer» B. first
Discussion
16.

The temperature dependence of reaction rate constant ( K ) by Arhenius law is given by

A. K ? e - E / RT
B. K ? e E / RT
C. K ? T . e - E / RT
D. K ? T . e - E / RT
Answer» B. K ? e E / RT
Discussion
17.

With increase in K 2 / K 1 in case of a unimolecular type elementary reactions , the fractional yield of ' R ' in mixed reactor (for a given conversion of ' A ')

A. decreases
B. increases
C. increases linearly
D. remains same
Answer» B. increases
Discussion
18.

If the pore diffusion controls in a catalytic reaction, the apparent activation energy E a is equal to

A. the intrinsic activation energy E .
B. ( E + E D ) where E D is activation due to diffusion.
C. ( E + E D )/2
D. E D /2
Answer» E.
Discussion
19.

The catalytic converter for conversion of SO 2 to SO 3 by contact process should have a feed with SO 2 content between

A. 2-5%
B. 7-10%
C. 12-15%
D. 20-25%
Answer» C. 12-15%
Discussion
20.

The decomposition of A into B is represented by the exothermic reaction, A 2 B . To achieve maximum decomposition, it is desirable to carry out the reaction.

A. at high P and high T.
B. at low P and high T.
C. at low P and low T.
D. at high P and low T.
Answer» D. at high P and low T.
Discussion
21.

The order of the chemical reaction, , whose rate equation is given as - rA = KC A 2 . C B is

A. 0
B. 1
C. 2
D. 3
Answer» E.
Discussion
22.

A space velocity of 5 hr -1 means that

A. five reactor volumes of feed (at specified conditions) are being fed into the reactor per hour.
B. after every 5 hours, reactor is being filled with the feed.
C. cent per cent conversion can be achieved in at least 5 hours.
D. a fixed conversion of a given batch of feed takes 5 hours.
Answer» B. after every 5 hours, reactor is being filled with the feed.
Discussion
23.

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

A. V / n
B. V
C. V . n
D. 1/ V
Answer» C. V . n
Discussion
24.

What is the order of chemical reaction , if itis found that the reaction rate doubles on doubling the concentration of B and also the reaction rate doubles when the concentrations of both A & B were doubled and quandrupled when the concentrations of both B & C were doubled ?

A. 1
B. 2
C. 3
D. 4
Answer» C. 3
Discussion
25.

For the liquid phase parallel reactions: R , r R = K 1 . C A 2 ; E 1 = 80 KJ/mole S , r s = K 1. C A ; E 2 = 120 KJ/mole The desired product is R. A higher selectivity of R will be achieved, if the reaction is conducted at

A. low temperature in a CSTR.
B. high temperature in a CSTR.
C. low temperature in a PFR.
D. high temperature in a PFR.
Answer» E.
Discussion
26.

A pollutant P degrades according to first order kinetics. An aqueous stream containing P at 2 kmole/m 3 and volumetric flow rate 1m 3 /h requires a mixed flow reactor of volume V to bring down the pollutant level to 0.5 kmole/m 3 . The inlet concentration of the pollutant is now doubled and the volumetric flow rate is tripled. If the pollutant level is to be brought down to the same level of 0.5 kmole/m 3 , the volume of the mixed flow reactor should be increased by a factor of

A. 7
B. 6
C. 3
D. 7/3
Answer» B. 6
Discussion
27.

For the gaseous reaction 2 A B , where the feed consists of 50 mole % A and 50 mole % inerts, the expansion factor is

A. 1
B. -0.5
C. -0.25
D. 0
Answer» D. 0
Discussion
28.

A non-catalytic chemical reaction of the type is called a __________ reaction.

A. parallel
B. series
C. series-parallel
D. none of these
Answer» D. none of these
Discussion
29.

The sequence in which three CSTR's of volumes 5, 10 and 15 m 3 will be connected in series to obtain the maximum production in a second order irreversible reaction is

A. 15, 10, 5
B. 5, 10, 15
C. 10, 5, 15
D. 10, 15, 5
Answer» B. 5, 10, 15
Discussion
30.

The following half life data are available for the irreversible liquid phase reaction A products. The overall order of reaction is

A. 0.5
B. 1
C. 1.5
D. 2
Answer» D. 2
Discussion
31.

The reaction rate almost gets doubled for 10°C rise in temperature. This is due to the fact that the

A. increased temperature reduces the activation energy.
B. fraction of molecules having threshold energy increases.
C. collision frequency increases.
D. value of threshold energy decreases.
Answer» C. collision frequency increases.
Discussion
32.

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).
Answer» E.
Discussion
33.

Half life period of a chemical reaction is proportional to C A 0 -1 , if the reaction is of __________ order.

A. first
B. zero
C. second
D. third
Answer» D. third
Discussion
34.

The gas phase reaction 2 A B is carried out in an isothermal plug flow reactor. The feed consists of 80 mole % A and 20 mole % inerts. If the conversion of A at the reactor exit is 50%, then C A / C A 0 at the outlet of the reactor is

A. 2/3
B. 5/8
C. 1/3
D. 3/8
Answer» C. 1/3
Discussion
35.

The value of ' n ' for a chemical reaction A B, whose reaction rate is C A 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
Answer» E.
Discussion
36.

With the same reaction time, initial concentration and feed rate, the reaction 2 A 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
Answer» B. higher in CSTR
Discussion
37.

On application of pressure to the equilibrium system, ice water ; which of the following phenomenon will occur ?

A. Water will evaporate
B. Equilibrium will not be attained
C. More ice will be formed
D. More water will be formed.
Answer» E.
Discussion
38.

The following gas phase reactions are carried out isothermally in a CSTR. A 2 R ; r 1 = k 1 p A ; k 1 = 20mole/(sec.m 3 bar) A 3 S ; r 2 = k 2 p A ; k 2 = 40mole/(sec.m 3 .bar) What is the maximum possible value of F R (mole/sec.) ?

A. 1/3
B. 1/2
C. 2/3
D. 2
Answer» D. 2
Discussion
39.

Pure A in gas phase enters a reactor 50% of this A is converted to B through the reaction, A 3 B . Mole fraction of A in the exit stream is

A. 1/2
B. 1/3
C. 1/4
D. 1/5
Answer» C. 1/4
Discussion
40.

For the reversible reaction A 2 B , if the equilibrium constant K is 0.05 mole/litre; starting from initially 2 moles of A and zero moles of B, how many moles will be formed at equilibrium ?

A. 0.253
B. 0.338
C. 0.152
D. 0.637
Answer» C. 0.152
Discussion
41.

The rate expression for the gaseous phase reaction, CO + 2H 2 CH 3 OH, is given by, . Which of the following is not possible ?

A. ? = 1, ? = 1, ? =1
B. ? = 1, ? = 2, ? = 1
C. ? = 1/3, ? = 2/3, ? = 1/3
D. ? = 1/2, ? = 1, ? = 1/2
Answer» B. ? = 1, ? = 2, ? = 1
Discussion
42.

The response curve for a step input signal from a reactor is called C -curve. The variance of C -curve in a 'tanks in series model' comprising of ' m ' tanks is equal to

A. m
B. 1/ m
C. m
D. m 2
Answer» C. m
Discussion
43.

The rate of the heterogenous catalytic reaction A ( g ) + B ( g ) C ( g ) is given by - r A = k . K A . p A . P B /(1 + K A . P A + K c . p c ), where K A and K c are the adsorption equilibrium constants. The rate controlling step for this reaction is

A. absorption of A .
B. surface reaction between absorbed A and absorbed B .
C. surface reaction between absorbed A and B in the gas phase.
D. surface reaction between A in the gas phase and absorbed B .
Answer» D. surface reaction between A in the gas phase and absorbed B .
Discussion
44.

For a __________ order chemical reaction, , the half life period is independent of the initial concentration of the reactant A .

A. zero
B. first
C. second
D. third
Answer» C. second
Discussion
45.

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 C x n , then what is the value of ' n ' ?

A. 4
B. 1/4
C. 16
D. 2
Answer» B. 1/4
Discussion
46.

The rate equation for the reaction represented by, is given by - r x = K 1 . C x /(1 + K 2 C x ). At high value of C x ( i.e .., K 2 C x > > 1), the order of the reaction and the rate constant are respectively

A. zero order & K 1 / K 2
B. zero order & K 1
C. first order & K 1
D. first order & K 1 / K 2
Answer» B. zero order & K 1
Discussion
47.

For the reaction, A + B 2 B + C ,

A. r A = r B
B. r A = - r B
C. r A = 2 r B
D. r A = r B /2
Answer» C. r A = 2 r B
Discussion
48.

The experimentally determined overall order of the reaction, A + B C + D , is two. Then the

A. reaction is elementary with a molecularity of 2.
B. molecularity of the reaction is 2, but the reaction may not be elementary.
C. reaction may be elementary with molecularity of 2.
D. reaction is elementary but the molecularity may not be 2.
Answer» B. molecularity of the reaction is 2, but the reaction may not be elementary.
Discussion
49.

The conversion in a mixed reactor/accomplishing a reaction A 3 R is 50% when gaseous reactant ' A ' is introduced at the rate of 1 litre/second and the leaving flow rate is 2 litres/second. The holding time for this operation is __________ second.

A. 0.5
B. 1
C. 2
D. 3
Answer» B. 1
Discussion
50.

Decomposition rate of a liquid ' X ' which decomposes as per the reaction is given by

A. K 1 . C X
B. ( K 1 + K 2 + K 3 ) C X
C. ( K 1 + K 2 ) C X
D. ( K 2 + K 3 ) C X
Answer» D. ( K 2 + K 3 ) C X
Discussion