Complex reactions & Approximations - Chemical Kinetics MCQs for CSIR UGC NET & GATE - Download PDF

Vijay Ishwar
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Complex reactions
Equilibrium & Steady State Approximation
MCQs for CSIR NET & GATE

Chemical Kinetics
Topic wise Assignment-5

QUIZ              PDF

Q1. The overall rate 𝑑[𝑃]/𝑑𝑡 for the reaction;

is given by
(a) K kf [A]2[C]
(b) K [A] [B]
(c) kf [B] [C]
(d) K kf [A]2[B] [C]

Q2. For the reaction scheme

The rate equation for formation of D is given as

[GATE 2003]

Q3. In a consecutive first order reaction,

Where k1 and k2 are respective rate constants, species B has transient existence. Therefore,
a) K1 ≈ k2
b) K1 = 2k2
c) K1 >> k2
d) K1 << k2

Q4. H2 and Br2 react o give HBr by the following steps

[GATE 2003]

The probable rate law for the above sequence is
a) Rate = k2 [H2][Br2]1/2
b) Rate = k2 [H2][Br2]
c) Rate = k2 K1/2 [H2][Br2]1/2
d) Rate = k2 [H2][Br]1/2

Q5. For the reaction of the type

[GATE 2004]

Given that [P]o = 1.0 M, k1 = 1x10-3 s-1 and k2 = 1x10-4 s-1, the time at which the concentrations of Q and R are 0.5966 M and 0.0355 M, respectively is
a) 500 s
b) 750 s
c) 1000 s
d) 1500 s

Q6. A reaction proceeds through the formation of an intermediate B in an unimolecular reaction

Q7. Using the steady state approximation the rate of the following reaction is

Q8. In the following sequence of reactions, the energy poor molecule A* in the assuming collision is robbed off, enough energy to be deactivated as

Q9. The reaction

Proceeds via the following steps

The rate of this reaction is equal to
a) 2 kb [NO] [O2]
b) (ka kb [NO]2 [O2] / (ka’ + kb [O2])
c) 2 kb [NO]2 [O2]
d) Ka [NO]2 [O2]

Statement linked answer type Q10 and Q11
The decomposition of ozone to oxygen 2O3(g) → 3O2(g); occurs by the mechanism

where M is the catalyst molecule. ki’ are rate constants and Ea,I’ the activation energies for the elementary steps.

Q10. Under the steady state approximation for the intermediates, the rae of decomposition of ozone -d[O3]/dt is

[GATE 2011]

Q11. Assuming k3 [O3] >> k2 [O2] [M], the activation energy of the overall reaction is

[GATE 2011]
a) (Ea,1 Ea,3) / Ea,2
b) Ea,3 + Ea,1 – Ea,2
c) Ea,2
d) Ea,1

Q12. For a reaction involving two steps given below

[GATE 2012]
First step: G ⇌ 2H
Second step: G + H → P
Assume that the first step attains equilibrium rapidly. The rate of formation of P is proportional to
a) [G]1/2
b) [G]
c) [G]2
d) [G]3/2

Q13. The overall rate of the following complex reaction by steady state approximation will be

[NET Dec 2011]

a) k1k2k3[A]3[B]
b) k2k1k3[A][B]3
c) k1k2k3[A][B]2
d) k1k2k3[A][B]

Q14. The rate equation for the reaction

[NET June 2013]
2AB + B2 → 2AB2
Is given by rate= k[AB][B2]
A possible mechanism consistent with rate law is

Q15. For the following chemical reaction

the rate constants k1 and k2 are at least 1000 times slower than either k3 or k4. During the course of the above reactions the ratio of the products B and C will be
a) [B]/[C] = k3/k4
b) [B]/[C] = k4/k3
c) [B]/[C] = k2k3/k1k4
d) [B]/[C] = k1/k2

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