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## SAMPLE QUESTIONS

1)     The time taken for the completion of 3/4 of a first order reaction is
(a) (2.303/k) log 3/4        (b) (2.303/k) log 4
(c) (2.303/k) log 1/4        (d) (2.303/0.75) log k
(e) (2.303/k) log 4/3

2)     In respect of the equation chemical kinetics, which one of the following statements is correct ?
(a) A is adsorption factor
(b) Ea is energy of activation
(c) R is Rydberg constant
(d) k is equilibrium constant

3)     75% of a substance disintegrates in 45 min (first order reaction).What is it's half life in minutes?
(a) 45 min                (b) 4.5 min
(c) 22.5 min                 (d) none of these

4)     What is the rate law for the following mechanism
O3 O2+ O              (Fast)
O3+O  2O2                (Slow)
(a) k [O2]             (b) k [O3]2         (c) k [O3] [O]         (d) none

5)     Which of the following formulae can be used to calculate population growth following first order kinetics?
(a) kt = 2.303 log           (b) kt = 2.303 log
(c) Pt = 2.303 log          (d) none of these

6)     The potential energy diagram for a reaction R  P is given below:

H° of the reaction corresponds to the energy
(a) a       (b) b             (c) c    (d) a + b

7)     For the reaction : 2A + B  C + D. Measurement of the rate of the reaction at varying concentrations are given below:
Trial No.         [A]            [B]           Rate (m mol L–1 s–1)
1.          0.010      0.010        2.5
2.          0.010      0.020         5.0
3.          0.030      0.020        45.0
The rate law therefore
(a) rate = k [A]2 [B]        (b) rate = k [A] [B]2
(c) rate = k [A] [B]          (c) rate = k [A]2 [B]2
(e) rate = k [A]3

8)     Under what conditions is the Arrhenius frequency factor equal to it's rate constant.
(a) Ea = zero                 (b) T = zero
(c) Ea = infinite           (d) T = infinite

9) The rate equation for the reaction 2A + B  C is found to be : rate = k [A] [B]. The correct statement in relation to this reaction is that the
(a) unit of k must be s–1
(b) t½ is constant
(c) rate of formation of C is twice the rate of      disapearance of A
(d) Value of k is independent of the initial concentration of A and B.

10)     Which one of the following equation is correct for the reaction:
N2(g) + 2H2(g)  2NH3(g) ?
(a)          (b)
(c)        (d)

11)    The reaction mechanism for the reaction P  R is as follows      P  Q (fast)
Q + P  R (slow)
The rate law for the main reaction (P  R) is
(a) k1 [P][Q]                (b) k1k2[P]
(c) k1k2[P]2             (d) k1k2[Q]

12)    In a chemical reaction A + B  Products, if the concentration of A and B are doubled, the rate of the reaction will
(a) be doubled           (b) become fourfold
(c) become sixfold             (d) be halved

13)     Rate of reaction A2 + 3B2  AB3 is found to be 10-2 mol/Lmin. The rate of disappearance of B2 and rate of formation of AB3 is
(a) 102, 10-2                     (b) 10-2, 10-1
(c) 10-2, 10-2                  (d) none

14)     The half life period for a first order reaction is 30 minutes. How long will it take for 1/32 of the reactant to be left behind?
(a) 60 min                 (b) 120 min
(c) 90 min                   (d) 150 min

15)     From the following data for the reaction between A and B
[A]                [B]    Initial rate (mol l-1 s-1)
mol l-1             mol l-1               300 K          320 K
2.5 X 10-4      3.0 X 10-5          5.0 X 10-4    2.0 X 10-3
5.0 X 10-4      6.0 X 10-5         4.0 X 10-3         --
1.0 X 10-3      6.0 X 10-5         1.6 X 10-2         --
Calculate the rate equation
(a) r = k[A][B]        (b) r = k[A]2[B]1
(c) r = k[A]2        (d) r = k[B]1

16)     A reaction proceeds in three stages. The first stage is a slow second order reaction, the second stage is fast and of the first order, the third stage is fast and is  third order reaction. The overall order of the reaction is
(a) first order        (b) second order
(c) third order        (d) zero order

17)     A drug becomes ineffective after 40% decomposition. It has rate constant k = 4.215 X 10-3 months-1. Assuming that decomposition of first order, calculate the expiry time of the drug in months.
(a) 119            (b) 122
(c) 244            (d) 238

18.    In a first order reaction, the concentration of the reactant, decreases from 0.8M to 0.4M is 15 minutes. The time taken for the concentration to change from 0.1 M to 0.025M is
(a) 7.5 minutes         (b) 15 minutes
(c)   30 minutes         (d) 60 minutes

19.  The half life period of radium is 1580 years. Calculate the time in years when 1/16 of radium of its initial concentration will remain be left behind
(a) 3160                           (b) 6320
(c) 4740                         (d) 790

20.    Consider the reaction,. When concentration of B alone was doubled, the half-life did not change. When the concentration of A alone was doubled, the rate increased by two times. The unit of rate constant for this reaction is
(a) s_1            (b) L mol_1s_1
(c) no unit             (d) mol L_1 s_

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