Complex reactions
Equilibrium & Steady State Approximation
MCQs for CSIR NET & GATE
Chemical Kinetics
Topic wise Assignment-5
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
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
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
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
Q11. Assuming k3 [O3] >> k2 [O2] [M], the activation energy of the overall reaction is
b) Ea,3 + Ea,1 – Ea,2
c) Ea,2
d) Ea,1
Q12. For a reaction involving two steps given below
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
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
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