Chemical Reaction Mcqs - Set 3

1)   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
Answer  Explanation 

ANSWER: Desorption of C

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: -0.5

Explanation:
No explanation is available for this question!


3)   Half life period of decomposition of a liquid ‘A’ by irreversible first order reaction is 12 minutes. The time required for 75% conversion of ‘A’ is _____________ minutes?

a. 18
b. 24
c. 6
d. 12
Answer  Explanation 

ANSWER: 24

Explanation:
No explanation is available for this question!


4)   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  Explanation 

ANSWER: All A., B. and C.

Explanation:
No explanation is available for this question!


5)   For identical flow rate and feed composition, X plug flow reactors (PER) in series with a total volume V gives the same conversion as single_______________?

a. CSTR of volume V
b. PFR of volume V
c. CSTR of volume V/X
d. PFR of volume V/X
Answer  Explanation 

ANSWER: PFR of volume V

Explanation:
No explanation is available for this question!


6)   Fractional conversion _________________ for an exothermic reversible chemical reaction, when the temperature is maximum?

a. Increases
b. Remains unchanged
c. Decreases
d. Unpredictable from the data
Answer  Explanation 

ANSWER: Decreases

Explanation:
No explanation is available for this question!


7)   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 does not entail a chain mechanism?

a. Proportional to
b. Independent of
c. Inversely proportional to
d. Proportional to the square of
Answer  Explanation 

ANSWER: Proportional to

Explanation:
No explanation is available for this question!


8)   For a packed bed reactor; the presence of a long tail in the residence time distribution curve is an indication of ?

a. Ideal plug flow
b. Bypass
c. Dead zone
d. Channelling
Answer  Explanation 

ANSWER: Dead zone

Explanation:
No explanation is available for this question!


9)   The use of space time is preferred over the mean residence time in the design of a/an____________________?

a. Batch reactor
b. Ideal tubular-flow reactor
c. Slurry reactor
d. CSTR
Answer  Explanation 

ANSWER: Ideal tubular-flow reactor

Explanation:
No explanation is available for this question!


10)   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  Explanation 

ANSWER: Diffusion within the pellet

Explanation:
No explanation is available for this question!


11)   Time required for 50% decomposition of a liquid in an isothermal batch reactor following first order kinetics is 2 minutes. The time required for 75% decomposition will be about _______________ minutes?

a. 3
b. 4
c. 6
d. 10
Answer  Explanation 

ANSWER: 4

Explanation:
No explanation is available for this question!


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  Explanation 

ANSWER: Exponentially with time

Explanation:
No explanation is available for this question!


13)   ‘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  Explanation 

ANSWER: V

Explanation:
No explanation is available for this question!


14)   Half life period of a chemical reaction is proportional to CA0 -1, if the reaction is of _______________ order?

a. First
b. Zero
c. Second
d. Third
Answer  Explanation 

ANSWER: Second

Explanation:
No explanation is available for this question!


15)   B.E.T. method of finding out surface area of a catalyst, uses the extension of _________________ isotherm?

a. Langmuir
b. Freundlich
c. Tempkin
d. None of these
Answer  Explanation 

ANSWER: Langmuir

Explanation:
No explanation is available for this question!


16)   Vegetable oils are hydrogenated in a _______________ reactor?

a. Slurry
b. Plug flow
c. Homogeneous catalytic
d. None of these
Answer  Explanation 

ANSWER: Slurry

Explanation:
No explanation is available for this question!


17)   In the hydrodealkylation of toluene to benzene, the following reactions occur: C7H8 + H2 → C6H6 + CH4 2C6H6 ⇌ C12H10 + H2 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  Explanation 

ANSWER: 0.144

Explanation:
No explanation is available for this question!


18)   Promoter_____________________?

a. Initiates a chemical reaction and is a catalyst by itself
b. Alters the position of equilibrium in a reversible reaction
c. Increases the number of active centres by increasing the unevenness of catalyst surface and by creating discontinuities in the crystals
d. All A., B. and C.
Answer  Explanation 

ANSWER: Increases the number of active centres by increasing the unevenness of catalyst surface and by creating discontinuities in the crystals

Explanation:
No explanation is available for this question!


19)   In an ideal P.F.R. at steady state conditions ___________________?

a. The composition of reactants remains constant along a flow path
b. The conversion of the reactant varies from point to point along a flow path
c. There is no lateral mixing of fluid
d. There may be diffusion along the flow path
Answer  Explanation 

ANSWER: The conversion of the reactant varies from point to point along a flow path

Explanation:
No explanation is available for this question!


20)   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  Explanation 

ANSWER: Fraction of molecules having threshold energy increases

Explanation:
No explanation is available for this question!


21)   The order of a chemical reaction is__________________?

a. An experimentally determined quantity
b. Always equal to the total stoichiometric number of reactants
c. Never fractional
d. None of these
Answer  Explanation 

ANSWER: An experimentally determined quantity

Explanation:
No explanation is available for this question!


22)   The rate of reaction does not decrease appreciably as the reaction proceeds in case of ______________ reactions?

a. Autocatalytic
b. Exothermic
c. Endothermic
d. Autothermal
Answer  Explanation 

ANSWER: Autocatalytic

Explanation:
No explanation is available for this question!


23)   Space time in flow reactor is____________________?

a. Usually equal to the residence time
b. The reciprocal of the space velocity
c. A measure of its capacity
d. Both A. and B.
Answer  Explanation 

ANSWER: Both A. and B.

Explanation:
No explanation is available for this question!


24)   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
Answer  Explanation 

ANSWER: Higher in P.F. reactor

Explanation:
No explanation is available for this question!


25)   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
Answer  Explanation 

ANSWER: Porosity is of less importance

Explanation:
No explanation is available for this question!


26)   The energy of activation of a chemical reaction ?

a. Is same as heat of reaction at constant pressure
b. Is the minimum energy which the molecules must have before the reaction can take place
c. Varies as fifth power of the temperature
d. Both B. and C.
Answer  Explanation 

ANSWER: Is the minimum energy which the molecules must have before the reaction can take place

Explanation:
No explanation is available for this question!


27)   For identical flow rate, feed composition and for elementary first order reactions, ‘N’ equal sized mixed reactors in series with a total volume ‘V’ gives the same conversion as a single plug flow reactor of volume ‘V’ for constant density systems. This is true, when the value of ‘N’ is ___________________?

a. 1
b. > 1
c.
d. ≥ 1
Answer  Explanation 

ANSWER: ∞

Explanation:
No explanation is available for this question!


28)   Which of the following does not produce a change in the value of rate constant of a reaction ?

a. Pressure
b. Temperature
c. Concentration and catalyst
d. None of these
Answer  Explanation 

ANSWER: Concentration and catalyst

Explanation:
No explanation is available for this question!


29)   The dispersion number of perfect mixed flow is__________________?

a. 0
b. > 150
c.
d. < 2100
Answer  Explanation 

ANSWER: ∞

Explanation:
No explanation is available for this question!


30)   In autocatalytic reactions ?

a. One of the reactants acts as a catalyst
b. One of the products acts as a catalyst
c. Catalysts have very high selectivity
d. No catalyst is used
Answer  Explanation 

ANSWER: One of the products acts as a catalyst

Explanation:
No explanation is available for this question!