Engineering Chemistry MCQ (Pseudo Order Reaction)

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Engineering Chemistry MCQ (Pseudo Order Reaction)

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1. Reactions which are bimolecular yet following ___________ order kinetics are called pseudo unimolecular reaction.
a) Zero
b) First
c) Second
d) Third
Answer: b
Explanation: Reactions that are bimolecular yet following first order kinetics are
called pseudo unimolecular reaction. Pseudo means pretentious. Inversion of cane sugar is an example of pseudo first order reaction.

2. Which of the following is an example of pseudo first order reaction?
a) Saponification of ester
b) Oxidation of hydrogen bromide
c) Gaseous decomposition of hydrogen iodide
d) Inversion of cane sugar
Answer: d
Explanation: Inversion of cane sugar is an example of pseudo first order reaction. All
the other options are not the example of pseudo first order reaction.

3. Which concentration plot is linear for a first order reaction? (A is one of the reactant)
a) [A] versus time
b) [A]2 versus time
c) Ln[A] versus time
d) √[A] versus time
Answer: c
Explanation: The ln[A] versus time plot is linear and other graphs are curved for a
first order reaction. For a zero order reaction, [A] versus time concentration plot is
linear. For a second order reaction, 1/[A] versus time concentration plot is linear.

4. Based on the collision model, the atoms at the top of the potential energy hill are called ___________
a) Transition state
b) Energetic atom
c) Steric factor
d) Activation energy
Answer: a
Explanation: Based on the collision model, the atoms at the top of the potential
energy hill are called transition state. The transition state is the state corresponding
to the highest energy along the reaction coordinate. It has more free energy in
comparison to the substrate or product; thus, it is the least stable state.

5. What does termolecular refer to?
a) 2 molecules colliding
b) 3 molecules colliding
c) 4 molecules colliding
d) 5 molecules colliding
Answer: b
Explanation: Termolecular means a collision of three molecules. Ter refers to three.

6. For a certain reaction, the rate = k[NO]2 [O2], when the initial concentration of NO is tripled, the initial rate ___________
a) Increases by a factor of nine
b) Increases by a factor of three
c) Increases by a factor of six
d) Decreases by a factor of nine
Answer: a
Explanation: For a certain reaction, the rate = k[NO]2[O2], when the initial
concentration of NO is tripled, the initial rate increases by a factor of nine. Here, the reaction is of the order 3.

7. In a series of reactions, the rate determining step is ___________
a) Simplest
b) Fast and complex
c) Fastest
d) Slowest
Answer: d
Explanation: In a series of reactions, the rate determining step is the slowest step.
The rate determining step is the slowest step of a chemical reaction that determines
the speed (rate) at which the overall reaction proceeds.

8. Threshold energy is the sum of ___________
a) Internal energy and external energy of reactants
b) Activation energy and external energy of reactants
c) Activation energy and internal energy of reactants
d) Activation energy and thermal energy
Answer: c
Explanation: Threshold energy is the sum of activation energy and internal energy of
reactants. The threshold energy for the production of a particle is the minimum
kinetic energy a pair of traveling particles must have when they collide.
Effect of Temperature on reaction rate