PROBLEM SOLVING

TECHNIQUES OF
PHYSICAL CHEMISTRY
FOR NEET

BY
JITENDRA HIRWANI

CHEMICAL KINETICS

ETOOSINDIA
INDIA’S NO. 1 ONLINE COACHING

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Kota, Rajasthan – 324005 Mob. : 9214233303
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INDIA’S NO. 1 ONLINE COACHING

BASIC EXERCISE
Rate of Reaction
1. Consider the chemical reaction :
N2(g) + 3H2(g)  2NH3(g)
The rate of this reaction can be expressed in terms of time of concentration of N2(g), H2(g) or NH3(g). Identify
the correct relationship amongst the rate expressions.
d N2  1 d H 2  1 d NH 3  d N2  3 d H 2  2 d NH 3 
(1) Rate =    (2) Rate =    
dt 3 dt 2 dt dt dt dt

d N2  1 d H 2  1 d NH 3  d N2  d H 2  d NH 3 

  (4) Rate =     

A
(3) Rate =
dt 3 dt 2 dt dt dt dt

I
Ans. (1)
2. In the formation of sulphur trioxide by the contact process 2SO2 (g) + O2(g) 2SO3(g) The rate of reaction

D
d  O2 
is expressed as – =2.5 × 10–4 mol L–1 sec–1. The rate of disappearance of (SO2) will be –
dt
(1) 5 × 10–4 mol L–1 S–1 (2) –2.25 × 10–4 mol L–1 S–1

N
(3) 3.75 × 10–4 mol L–1 S–1 (4) 50.0 × 10–4 mol L–1 S–1

I
Ans. (1)

3. In a catalytic reaction involving the formation of ammonia by Haber's process N2 + 3H2 2NH3 the rate of appearance

S
of NH3 was measured as 2.5×10–4 mole L–1 S–1 The rate of disappearance of H2 will be –
(1) 2.5 × 10–4 mol L–1 S–1 (2) 1.25 × 10–4 mol L–1 S–1
(3) 3.75 × 10–4 mol L–1 S–1 (4) 5 × 10–4 mol L–1 S–1

O
Ans. (3)

4. Which of the following statement is correct for a reaction X + 2Y  Product

(1) The rate of disappearance of X = twice the rate of disappearance of Y.

O
(2) The rate of disappearance of X = ½ rate of appearance of products
(3) The rate of appearance of products = ½ the rate of disappearance of Y

T
(4) The rate of appearance of products = ½ the rate of disappearance of X
Ans. (3)

E
5. For the reaction, N2O5 2NO2 + ½ O2
d[N2 O 5 ] d[NO 2 ]
Given   K1 [N2 O 5 ] , =K2[N2O5]
dt dt
d[O 2 ]
=K3[N2O5]
dt
The relation between K1 , K2 and K3 is –
(1) 2K1 = K2 = 4K3 (2) K1 = K2 = K3 (3) 2K1 = 4K2 = K3 (4) None
Ans. (1)

6. Rate of formation of SO3 according to the reaction 2SO2+O2 2SO3 is 1.6 × 10–3 kg.min–1 Hence rate at which
SO2 reacts is :–
(1) 1.6 × 10–3 kg. min–1 (2) 8.0 × 10–4 kg. min–1
(3) 3.2 × 10–3 kg. min–1 (4) 1.28 × 10–3 kg. min–1
Ans. (4)

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7. For a general chemical change 2A+3B  products, the rate of disappearance of A is r 1 and of B is r2. The rates
r1 and r2 are related as :–
(1) 3r1 = 2r2 (2) r1 = r2 (3) 2r1 = 3r2 (4) r12 = 2r22
Ans. (1)
8. For the reaction 4A + B  2C + 2D
The statement not correct is :–
(1) The rate of disappearance of B is one fourth the rate of disappearance of A
(2) The rate of appearance of C is half the rate of disappearance of B
(3) The rate of formation of D is half the rate of consumption of A
(4) The rates of formation of C and D are equal

A
Ans. (2)

I
9. In a reaction N2(g) + 3H2(g)  2NH3(g) the rate of appearance of NH3 is 2.5× 10-4mol L-1 sec-1. The Rate
of reaction & rate of disappearance of H2 will be (In mol L-1 sec.-1)
(1) 3.75 × 10–4, 1.25 × 10–4 (2) 1.25 × 10–4, 2.5 × 10–4

Ans.
(3) 1.25 × 10–4, 3.75 × 10–4
(3)

N D
(4) 5.0 × 10–4, 3.75 × 10–4

I
10. For gaseous reaction, rate = k [A] [B]. If volume of container is reduced to of initial, then the rate of the
4
reaction will be....... times of initial:-

S
1 1
(1) (2) 8 (3) (4) 16
8 16
Ans. (4)

11.

O O
Rate Law / Order / Molecularity
If the concentration units are reduced by n times then the value of rate constant of first order will
(1) Increases by n times
(3) Not change
(2) Decreases by factor of n
(4) None

T
Ans. (3)
12. The rate of certain hypothetical reaction
A + B + C products is given by

E
d A  1 1 1
r= =K A  2 B  3 C  4 The order of the reaction –
dt

1 13
(1) 1 (2) (3) 2 (4)
2 12
Ans. (4)
13. Which of the following rate law has an overall order of 0.5 for reaction involving substances x,y and z ?

(1) Rate = K (Cx) (Cy) (Cz) (2) Rate = K (Cx)0.5(Cy)0.5(Cz)0.5

(3) Rate = K (Cx)1.5 (Cy)–1(Cz)° (4) Rate = K(Cx)(Cz)° / (Cy)2
Ans. (3)
14. A chemical reaction involves two reacting species. The rate of reaction is directly proportional to the conc. of
one of them and inversely proportional to the concentration of the other. The order of reaction is –
(1) 1 (2) 2 (3) Zero (4) Unpredictable
Ans. (3)

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15. For the reaction H2(g) + Br2(g) 2HBr(g), the experimental data suggests, Rate = K [H2] [Br2]½. The molecularity
and order of reaction for the reaction is –
(1) 2 and 2 respectively (2) 2 and 1½ respectively
(3) 1½ and 2 respectively (4) 1½ and 1½ respectively
Ans. (2)
16. Select the rate law that corresponds to the data shown for the following reaction A + B  C
Exp. [A] [B] Initial rate
1. 0.012 0.035 0.10
2. 0.024 0.070 1.6
3. 0.024 0.035 0.20
4. 0.012 0.070 0.80

A
(1) Rate = K [B]3 (2) Rate = K[B]4 (3) Rate = K[A][B]3 (4) Rate = K[A]2[B]2

I
Ans. (3)

17. In a certain gaseous reaction between X and Y, X + 3Y XY3 The initial rates are reported as follows –
[X] [Y] Rate

D
0.1 M 0.1M 0.002 Ms–1
0.2 M 0.1 M 0.002 Ms–1

N
0.3 M 0.2 M 0.008 Ms–1

I
0.4 M 0.3 M 0.018 Ms–1
The rate law is –
(1) r = K[X][Y]3 (2) r = K[X]°[Y]2 (3) r = K[X][Y] (4) r = [X]°[Y]3

S
Ans. (2)

18. Select the law that corresponds to date shown for the following reaction 2A + B  C + D –
Exp. [A] [B] Initial rate

O
(mol L–1 min–1)
1. 0.1 0.1 7.5 × 10–3
2. 0.3 0.2 9.0 × 10–2

O
3. 0.3 0.4 3.6 × 10–1
4. 0.4 0.1 3.0 × 10–2

T
(1) Rate = K [A]2[B] (2) Rate = K[A][B]2 (3) Rate = K[A][B]3 (4) Rate = K[A][B]
Ans. (2)

19. For a hypothetical reaction ; A + B  C the following data was obtained in three different experiments :–

E
[A] [B] Rate or reaction
(mol lit–1) (mol lit–1) (mol lit–1 min–1)
0.01 0.01 1.0  10–4
0.01 0.03 9.0  10–4
0.03 0.03 2.70  10–3
Suggest rate law :–
(1) r = K[A]2 [B] (2) r = K[A] [B]2 (3) r = K[A] [B] (4) None of these
Ans. (2)
20. Calculate the order of the reaction in A and B :
[A] (mol l-1) [B] (mol-1) Rate
0.05 0.05 1.2 × 10–3
0.10 0.05 2.4 × 10–3
0.05 0.10 1.2 × 10–3
(1) 1 and 0 (2) 1 and 1 (3) 0 and 1 (4) None
Ans. (1)

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21. For a chemical reaction A + B product, the order is one with respect to each A and B. Value of x and y from
the given data is :–
Rate (mole/lit./sec.) (A) (B)
0.10 0.20 M 0.05 M
0.40 x 0.05 M
0.80 0.40 M y
(1) 0.20, 0.80 (2) 0.80, 0.40 (3) 0.80, 0.20 (4) 0.40, 0.20
Ans. (3)

22. Time required to complete a half fraction of a reaction varies inversely to the concentration of reactant then
the order fo reaction is –

Ans.

23.
(1) Zero
(3)
(2) 1 (3) 2

The rate law for the single step reaction 2A + B  2C, is given by –
(4) 3

I A
D
(1) Rate = K[A][B] (2) Rate = K[A]2[B]
(3) Rate = K[2A][B] (4) Rate = K[A]2[B]°

N
Ans. (2)

I
24. Following mechanism has been proposed for a reaction.
2A + B  D + E

S
A + B  C + D – (slow)
A + C E – – (fast) The rate law expression for the reaction is –
2
(1) r = K[A] [B] (2) r = K[A] [B]

O
(3) r = K[A]2 (4) r = K[A][C]
Ans. (2)
25. For a reaction of the type A + B  products, it is observed that doubling the concentration of A causes the

O
reaction rate to be four times as great, but doubling the amount of B does not effect the rate. The rate equation
is –

T
(1) Rate = K [A][B] (2) Rate = K [A]2 (3) Rate = K[A]2[B] (4) Rate = K[A]2[B]2
Ans. (2)
26. Point out incorrect statement.

E
(1) Rate law is an experimental valve
(2) Law of mass action is a theoretical proposal
(3) Rate law is more informative than law of mass action for developing mechanism
(4) Rate law is always different from the expression of law of mass action.
Ans. (4)
27. For a chemical reaction A  B it is found that the rate of reaction double when the concentration of A is increased
four times. The order in A for this reaction is –
(1) Two (2) One (3) Half (4) Zero
Ans. (3)

28. For an elementary process 2X + Y Z + W, the molecularity is –

(1) 2 (2) 1 (3) 3` (4) Unpredictable
Ans. (3)

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d P  2
29. The rate law of the reaction A + 2B product is given by  K A  B  . If A is taken in large excess,
dt
the order of the reaction will be –
(1) Zero (2) 1 (3) 2 (4) 3
Ans. (2)

30. The decomposition of N2O5 occurs as,

2N2O5 4NO2 + O2, and follows first order kinetics; hence

(1) The reaction is bimolecular (2) The recation is unimolcular
(3) t1/2 a° (4) None

A
Ans. (3)

I
31. The accompanying figure depicts the change in concentration of species X and Y for the reaction X Y as
a function of time the point of intersection of the two curves reperesents.

D
Concentration

Time

I Fig.
N
Ans.
32.
(1) t1/2
(3) t2/3
(1)

O S
(2) t3/4
(4) Data insufficient to predict

For a reaction A + B products, the rate of the reaction was doubled when the concentration of A was doubled,
the rate was again doubled when the conc. of A & B were doubled the order of the reaction with respect to

O
A & B are:–
(1) 1, 1 (2) 2, 0 (3) 1, 0 (4) 0, 1
Ans. (3)

33.

Ans.

34. E T
For the reaction A + B  products, it is found that the order of A is 1 and the order of B is

conc. of both A and B are increased four times, the rate will increase by a factor of :–
(1) 16
(2)
(2) 8

The rate law for a reaction A + B  product is

(3) 6 (4) 4
1
2
. When the

rate = K[A]1 [B]2. Then which one of the following statements is false :–
(1) If [B] is held constant while [A] is doubled, the reaction will proceed twice as fast
(2) If [A] is held constant while [B] is reduced to one quarter, the rate will be halved
(3) If [A] and [B] are both doubled, the reaction will proceed 8 times as fast
(4) This is a third order reaction
Ans. (2)
35. For a chemical reaction A  B, the rate of reaction doubles when the conc. of A is increased 8 times. The order

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of reaction w.r.t. A is :–

1 1
(1) 3 (2) (3) (4) Zero
2 3
Ans. (3)
36. The specific rate constant of a first order reaction depends on the :–
(1) Conc. of the reactant (2) Conc. of the product
(3) Time (4) Temperature
Ans. (4)

Pseudo First Order Reaction / Mechanism of Reaction

37. The hypothetical reaction A2 + B2  2AB follows the mechanism as given below –


A2  A + A ............. (fast)

A + B2  AB + B ............. (slow)
A + B  AB ............. (fast)

I A
D
The order of the over all reaction is –
(1) 2 (2) 1 (3) 1½ (4) Zero

N
Ans. (3)

38.

Ans.
39.
(1)
(2) 1

The acid hydrolysis of ester is –

I
For reaction NO2 + CO  CO2 + NO, the rate expression is, Rate = K [NO2]2
The number of molecules of CO involved in the slowest step will be –
(1) 0

S
(3) 2 (4) 3

O
(1) I order reaction (2) Bimolecular reaction
(3) Pseudo unimolecular reaction (4) All

O
Ans. (4)
40. In the sequence of reaction

T
K1 K2 K3
A 
 B 
 C 
 D;
K3 > K2 > K1, then the rate determining step of the reaction is :–
(1) A B (2) C  D (3) B  C (4) A  D

E
Ans. (1)
41. The reaction mechanism for the reaction P R is as follows :–
K

P 
1

 2Q (fast) ; 2Q + P 
K2
 R (slow)

the rate law for the main reaction (P R) is :–

(1) K1[P] [Q] (2) K1K2[P] (3) K1K2[P]2 (4) K1K2[a]
Ans. (3)
42. The reaction 2A + B  products, follows the mechanism



2A  A2 (fast)
A2 + B  P (slow)
The order of the reaction is :–
(1) 1.5 (2) 3 (3) 1 (4) 2
Ans. (2)

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43. For the reaction 2NO + Cl2  2NOCl the following mechanism has been proposed



NO + Cl2  NOCl2 (fast)
NOCl2 + NO 2NOCl (slow) the rate law for the reaction is :-
(1) Rate = K[NO]2[Cl2] (2) Rate = K[NO][Cl2]2
(3) Rate = K[NOCl2] (4) Rate = K[NOCl]2
Ans. (1)

Zero / First / nth Order Reaction

44. K for a zero order reaction is
2 × 10–2 mol L–1 sec–1. If the concentration of the reactant after 25 sec is 0.5 M, the initial concentration must

A
have been.

I
(1) 0.5 M (2) 1.25 M (3) 12.5 M (4) 1.0 M
Ans. (4)
45. If the first order reaction involves gaseous reactants and gaseous products the units of its rate are –

D
(1) atm. (2) atm - sec. (3) atm – sec–1 (4) atm2 sec2
Ans. (3)

N
46. Plot of log(a – x) vs time t is straight line. This indicates that the reaction is of –

I
(1) Second order (2) First order (3) Zero order (4) third order
Ans. (2)
47. The units for the rate constant of first order reaction is –

S
(1) s–1 (2) mol L–1 s–1 (3) mol s–1 (4) Lmol–1 s–1
Ans. (1)

48. The rate constant of a first order reaction is 4 × 10–3 sec–1. At a reactant concentration of

O
0.02 M, the rate of reaction would be–
(1) 8 × 10–5 M sec–1 (2) 4 × 10–3 M sec–1
(3) 2 × 10–1 M sec–1 (4) 4 × 10–1 M sec–1

O
Ans. (1)
49. In a first order reaction the concentration of the reactant is decreased from 1.0 M to 0.25 M in 20 min. The rate

T
constant of the reaction would be –
(1) 10 min–1 (2) 6.931 min–1 (3) 0.6931 min–1 (4) 0.06931 min–1

E
Ans. (4)

50. In a first order reaction the a/(a – x) was found to be 8 after 10 minute. The rate constant is

(1)  2.30 3  3 log 2  (2)  2.30 3  2 log 3  (3) 10 × 2.303 × 2log3 (4) 10 × 2.303 × 3log2
10 10
Ans. (1)

51. 75% of a first order reaction was found to complete in 32 min. When will 50% of the same reaction complete–
(1) 24 min (2) 16 min (3) 8 min (4) 4 min
Ans. (2)
52. A first order reaction has a half life period of 69.3 sec. At 0.10 mol lit–1 reactant concentration rate will be –
(1) 10–4 M sec–1 (2) 10–3 M sec–1 (3) 10–1 M sec–1 (4) 6.93 × 10–1 M sec–1
Ans. (2)
53. What fraction of a reactant showing first order remains after 40 minute if t½ is 20 minute :
(1) 1/4 (2) 1/2 (3) 1/8 (4) 1/6
Ans. (1)

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54. For a first order reaction A  products, the rate of reaction at [A] = 0.2 M is 1× 10–2 mol lit–1min–1. The half life
period for the reaction is –
(1) 832 min. (2) 440 sec. (3) 416 min. (4) 14 min.
Ans. (4)
55. The half life for the first order reaction
N2O5  2NO2 + ½ O2 is 24 hrs. at 30°C. Starting with 10g of N2O5 how many grams of N2O5 will remain after
a period of 96 hours ?
(1) 1.25 g (2) 0.63 g (3) 1.77 g (4) 0.5 g
Ans. (2)
56. What is the half life of a radioactive substance if 87.5% of any given amount of the substance disintegrate in

A
40 minutes ?

I
(1) 160 min (2) 10 min (3) 20 min (4) 13 min 20 sec.
Ans. (4)

D
57. For a given reaction of first order it takes 20 minute for the concentration to drop from 1 M to 0.6 M. The time
required for the concentration to drop from 0.6 M to 0.36 M will be :
(1) More than 20 min (2) Less than 20 min (3) Equal to 20 min (4) Infinity

N
Ans. (3)

I
58. A first order reaction is carried out with an initial concentration of 10 mole per litre and 80% of the reactant
changes into the product. Now if the same reaction is carried out with an initial concentration of 5 mol per litre

S
for the same period the percentage of the reactant changing to the product is.
(1) 40 (2) 80 (3) 160 (4) Cannot be calculated
Ans. (2)

O
59. In the following first order completing reaction.
A + Reagent  Product, B + Reagent  Product
The ratio of K1 / K2 if only 50% of B will have been reacted, When 94% of A has been reacted is –

O
(1) 4.06 (2) 0.246 (3) 2.06 (4) 0.06
Ans. (1)

T
60. The reaction L M is started with 10 g of L. After 30 and 90 minute, 5 g and 1.25 g of L are left respectively.
The order of reaction is

E
(1) 0 (2) 2 (3) 1 (4) 3
Ans. (3)
61. If doubling the initial concentration of a reactant doubles t½ of the reaction, the order of the reaction is–
(1) 3 (2) 2 (3) 1 (4) 0
Ans. (4)
62. The half life period for calalytic decomposition of AB3 at 50 mm is found to be 4 hrs and at 100 mm it is 2 hrs.
The order of reaction is –
(1) 3 (2) 1 (3) 2 (4) 0
Ans. (3)
63. The rate constant for a reaction is 10.8 × 10–5 mol L–1 S–1 The reaction obeys –
(1) First order (2) Zero order (3) Second order (4) All are wrong
Ans. (2)

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64. A substance 'A' decomposes in solution following the first order kinetics flask I contains 1 lit of
1M. solution of A and flask II contains. 100 ml of 0.6 M solution. After 8 hr. the concentration of A in flask.
I become 0.25 M, what will be the time for concetration of A in flask II to become 0.3 M.
(1) 0.4 hr. (2) 2.4 hr.
(3) 4.0 hr. (4) Unpredictable as rate constant is not given
Ans. (3)
65. The rate constant (K) for the reaction 2A + B  product was found to be 2.5 × 10–5 litre mol–1 sec–1 after
15 sec, 2.60 × 10–5 lit mol–1 sec–1 after 30 sec and 2.55 × 10–5 lit mol–1 sec–1 after 50 sec. The order of reaction
is
(1) 2 (2) 3 (3) Zero (4) 1
Ans. (1)

66.

Ans.
If a reaction with t½ = 69.3 second; has a rate constant 10–2 per second the order is :
(1) Zero
(2)
(2) 1 (3) 2 (4) 3

I A
67.
1M solution to be reduced to 0.5 M.

(1) 8.665 × 103 min (2) 8 × 10–3 min

N D
The rate constant for a second order reaction is 8 × 10 –5 M –1 min –1 : How long will it take a

(3) 1.25 × 104 min (4) 4 × 10–5 min

I
Ans. (3)

68. A graph between t1/2 and conc. for nth order reaction is a straight line. Reaction of this nature is completed 50%

S
in 10 minutes when conc. is 2 mol L–1. This is decomposed 50% in t minutes at 4 mol L–1 n and t are respectively

(1) 0, 20 min.
(2) 1, 10 min.

O
(3) 1, 20 min.
(4) 0, 5 min. t½

Ans.

69.
(2)

TO Fig. conc.

In the first order reaction 75% of the reactant disappeared in 1.388 h. Calculate the rate constant of the reaction:–

E
(1) 1 s–1 (2) 2.8 × 10–4 s–1 (3) 17.2 × 10–3 s–1 (4) 1.8 × 10–3 s–1
Ans. (2)
70. In the case of first order reaction, the ratio of time required for 99.9% completion to 50% completion is :–
(1) 2 (2) 5 (3) 10 (4) None
Ans. (3)
71. From different sets of data of t 1/2 at different initial concentrations say 'a' for a given reaction, the
[t1/2  a] is found to be constant. The order of reaction is :–
(1) 0 (2) 1 (3) 2 (4) 3
Ans. (3)
72. The reaction 2N2O5(g) 4NO2(g) + O2(g)
is first order with respect to N2O5. Which of the following graph would yield a straight line :–
(1) log(PN2O5) versus time with – Ve slope (2) (PN2O5)–1 versus time
(3) (PN2O5) versus time (4) log(PN2O5) versus time with + Ve slope
Ans. (1)

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73. Which of the following curves represents a Ist order reaction :–

(1) log (a-x) (2) log (a-x)

t 1/ t

(3) t ½ (4) 1 & 3 both

a
Ans. (4)

A
74. The following data were obtained at a certain temperature for the decomposition of ammonia

I
p (mm) 50 100 200
t1/2 3.64 1.82 0.91

D
The order of the reaction is :–
(1) 0 (2) 1 (3) 2 (4) 3
Ans. (3)

75.
is tripled
(1) 3 (2) 9

I(3) x
N
A reaction is found to have the rate constant x sec–1 by what factor the rate is increased if initial conc. of A

(4) Remains same

S
Ans. (1)

76. The half life of a first order reaction is 10 min. If initial amount is 0.08 mol/lit. and conc. at some instant is 0.01
mol/lit. then t =

O
(1) 10 min. (2) 30 min. (3) 20 min. (4) 40 min.
Ans. (2)

O
77. Which is incorrect :–
(1) Half life of a first order reaction is independent of initial concentration

T
(2) Rate of reaction is constant for first order reaction
(3) Unit of K for second order reaction is mol–1 lit sec–1
(4) None

E
Ans. (2)

78. Hydrolysis of ester in alkaline medium is :–

(1) First order reaction with molecularity one
(2) Second order reaction with molecularity two
(3) First order reaction with molecularty two
(4) Second order reaction with molecularity one
Ans. (2)

1
79. The expression which gives th life of Ist order reaction is :–
4

K 4 2.303 2.303 3 2.303 4

(1) log (2) log 3 (3) log (4) log
2 .3 0 3 3 K K 4 K 3
Ans. (4)

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80. The rate constant of a zero order reaction is 0.2 mol dm-3h-1. If the concentration of the reactant after 30 minutes
is 0.05 mol dm-3. Then its initial concentration would be :-

(1) 6.05 mol dm-3 (2) 0.15 mol dm-3 (3) 0.25 mol dm-3 (4) 4.00 mol dm-3
Ans. (2)
81. A reaction is of first order. After 100 minutes 75 gm of the reactant A are decomposed when
100 gm are taken initially, calculate the time required when 150 gm of the reactant A are decomposed, the initial
weight taken is 200 gm :-
(1) 100 minutes (2) 200 minutes (3) 150 minutes (4) 175 minutes
Ans. (1)
82. For which of the following, the unit of rate and rate constant of the reaction are identical :-

A
(1) First order reaction (2) Zero order reaction

I
(3) Second order reaction (4) Fractional order of reaction
Ans. (2)

D
83. 2A  Product, follows the first order kinetics. If the half life period of the reaction at
[A]Initial = 0.2 mole lit–1 is 20 min. then the value of rate constant would be:-
(1) 4 sec. (2) 20 sec. (3) 4 lit. mol–1 min.–1 (4) None of these

N
Ans. (4)

84. Correct statement about first order reaction is:-

(1) tcomplition = finite

(3) Unit of K is mole lit–1 sec–1

S I
(2) t1/2 
1
a

(4) t1/2 × K = const. at const. temp.

O
Ans. (4)

Collision Theory and Factors Affecting Rate

85.

O
According to collision theory of reaction rates –
(1) Every collision between reactant leads to chemical reaction

T
(2) Rate of reaction is proportional to velocity of molecules
(3) All reactions which occur in gaseous phase are zero order reaction

E
(4) Rate of reaction is directly proportional to collision frequency.
Ans. (4)

86. Activation energy of a reaction is –

(1) The energy released during the reaction
(2) The energy evolved when activated complex is formed
(3) Minimum amount of energy needed to overcome the potential barrier of reaction
(4) The energy needed to form one mole of the product
Ans. (3)

87. The minimum energy for molecules to enter into chemical reaction is called.
(1) Kinetic energy (2) Potential energy (3) Threshold energy (4) Activation energy
Ans. (3)

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88. The rate constant K1 of a reaction is found to be double that of rate constant K2 of another reaction. The
relationship between corresponding activation energies of the two reactions at same temperature (E1 & E2) can
be represented as
(1) E1 > E2 (2) E1 < E2 (3) E1 = E2 (4) E1 = 4E2
Ans. (2)

89. At room temperature the reaction between NO and O2 to give NO2 is fast while that between CO and O2 is slow
it is due to –
(1) CO is smaller in size than that of NO
(2) CO is poisonous
(3) The activation energy for the reaction

A
2NO + O2 2NO2 is less than 2CO + O2 2CO2

I
(4) None
Ans. (3)

90. Chemical reaction occurs as a result of collision between reacting molecules. Therefore the reaction rate is given

D
by
(1) Total number of collisions occuring in a unit volume per second
(2) Fraction of molecules which possess energy less than the threshold energy.

N
(3) Total number of effective collisions

I
(4) None
Ans. (3)

S
91. An endothermic reaction A  B have an activation energy 15 K cal/mol and the heat of the reaction is 5 K
cal/mol. The activation energy of the reaction B  A is –
(1) 20 k cal/mol (2) 15 kcal/mol (3) 10 kcal/mol (4) Zero

O
Ans. (3)
92. For A + B  C + D;  H = –20 kJ mol –1 . The activation energy of the forward reaction is.
85 KJmol–1. The activation energy for backward reaction is ____________ KJ mol–1.

O
(1) 65 (2) 105 (3) 85 (4) 40
Ans. (2)

T
93. A large increase in the rate of a reaction for a rise in temperature is due to –
(1) Increase in the number of collisions
(2) Increase in the number of activated molecules

E
(3) Lowering of activation energy
(4) Shortening of the mean free path
Ans. (2)
94. Rate of which reactions increases with temperature –
(1) Of any (2) Of exothermic reaction
(3) Of endothermic reaction (4) Of None
Ans. (1)
95. The rate of a chemical reaction doubles for every 100C rise in temperature. If the temp is increased by 600C the
rate of reaction increases by :
(1) 20 times (2) 32 times (3) 64 times (4) 128 times
Ans. (3)

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96. According to the arrhenius equation a straight line is to be obtained by plotting the logarithm of the rate constant
of chemical reaction (log k) against.

(1) (T) (2) log T (3) 1 T (4) log 1 T

Ans. (3)

97. Which plots will give the value of activation energy.

(1) K sT (2) 1 K sT (3) lnK sT (4) lnK s 1 T

Ans. (4)

98. Given that K is the rate constant for some order of any reaction at temp T then the value of Tlim

log K _________.

A
(1) A 2.303 (2) A (3) 2.303 A (4) log A

I
Ans. (4)

99. From the following data; the activation energy for the reaction (cal/mol) H2 + I2  2HI

D
T , (in, K) 1/T, (in, K–1) log10K
769 1.3 × 10–3 2.9
667 1.5 × 10–3 1.1

Ans.

100.
(1) 4 × 104
(1)
(2) 2 × 104

I N
(3) 8 × 104 (4) 3 × 104

The rate constant; the activation energy and the arrhenius parameter of a chemical reaction at 25 0C are

S
3 × 10–4 sec–1; 104.4 KJ mol–1 and 6.0 × 1014 sec–1 respectively, the value of the rate constant as T  is.
(1) 2 × 108 sec–1 (2) 6 × 1014 sec–1 (3) Infinity (4) 3.6 × 1030 sec–1
Ans. (1)

101.

Ans. O
For an endothermic reaction where H represents the enthalpy of the reaction in KJ/mol ; the minimum value
for the energy of activation will be

O
(1) Less than H
(3)
(2) Zero (3) More than H (4) Equal to H

T
102. The rate of reaction increases by 2.3 times when the temperature is raised from 300 K to 310 K. If K is the rate
constant at 300 K then the rate constant at 310 K will be equal to –
(1) 2K (2) K (3) 2.3 K (4) 3K2

E
Ans. (3)

103. If concentration of reactants is increased by 'x' then the K becomes –

K K
(1) ln (2) (3) K + x (4) K
x x
Ans. (4)

104. Which is used in the determination of reaction rates.

(1) Reaction Temperature (2) Reaction Concentration
(3) Specific rate constant (4) All of these
Ans. (4)

105. The rate constant of a first order reaction depends on the :–

(1) Concentration of the reactant (2) Concentration of the product
(3) Time (4) Temperature
Ans. (4)

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106. For the decomposition of N2O5(g) it is given that–

1
2N2O5(g)4NO2(g) + O2(g) activation energy = Ea N2O5(g)2NO2(g) + O (g) activation energy = Ea' then
2 2
(1) Ea = 2Ea' (2) Ea > Ea' (3) Ea < Ea' (4) Ea = Ea'
Ans. (4)
107. For a reaction for which the activation energies of forward and reverse reactions are equal :–
(1) H = 0 (2) S = 0 (3) The order is zero (4) There is no catalyst
Ans. (1)

108. The energy of activation of a forward reaction is 50 Kcal. The energy of activation of its backward reaction
is:–

A
(1) Equal to 50 Kcal. (2) Greater than 50 Kcal.

I
(3) Less than 50 Kcal. (4) Either greater or less than 50 Kcal.
Ans. (4)

D
109. An exothermic reaction X  Y has an activation energy 30 KJ mol–1. If energy change (E) during the reaction
is – 20 KJ, then the activation energy for the reverse reaction is :–
(1) 10 KJ (2) 20 KJ (3) 50 KJ (4) – 30 KJ

N
Ans. (3)

I
110. Which of the following plot is in accordance with the arrhenius equation :–

S
(1) log K (2) log K (3) log K (4) K

T 1 1 1

O
T T T
Ans. (3)
111. For a certain gaseous reaction a 10° C rise of temp. from 25° C to 35° C doubles the rate of reaction. What is

O
the value of activation energy :–
10 2.303  10
(1) (2)

T
2.303R  298  308 298  308 R

0.693R  10 0.6 93 R  29 8  30 8
(3) (4)
290  308 10

E
Ans. (4)
112. The activation energy for the forward reaction X  Y is 60 KJ mol-1 and H is - 20 KJ mol-1. The activation energy
for the backward reactionY  X is:-
(1) 80 KJ mol-1 (2) 40 KJ mol-1 (3) 60 KJ mol-1 (4) 20 KJ mol-1
Ans. (1)
113. For producing the effective collisions, the colloiding molecules must posses:-
(1) A certain minimum amount of energy
(2) Energy equal to or greater than threshold energy
(3) Proper orientation
(4) Threshold energy as well as proper orientation of collision
Ans. (4)

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114. The half life for a reaction is --------of temperature:-

(1) Independent (2) Increased with increase
(3) Decreased with increase (4) Increased or decreased with increase
Ans. (3)
115. The activation energy for a chemical reaction depends upon :-
(1) Temperature (2) Nature of reacting species
(3) Concentration of the reacting species (4) Collision frequency
Ans. (2)

116. The rate of reaction increases by the increase of temperature because :–

(1) Collision is increased

A
(2) Energy of products decreases

I
(3) Fraction of molecules possessing energy  ET (Threshold energy) increases
(4) Mechanism of a reaction is changed
Ans. (3)

N D
S I
O O
E T

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ANALYTICAL EXERCISE
1. Consider the data below for a reaction A  B
Time
0 10 20 30
(sec)
-2 2 -2 -2
Rate 1.60×10 1.60×10 1.60×10 1.59×10
From the above data the order of reaction is
(1) Zero (2) 1 (3) 2 (4) 1
Ans. (1)
1

A
2. The graph between the log K versus is a straight line. The slope of the line is
T

I
2.303R Ea 2.303R Ea
(1)  Ea (2)  (3) Ea (4)
2.303R 2.303R

D
Ans. (2)
3. The temperature coefficient for most of the reaction lies between

N
(1) 1 & 3 (2) 2 & 3 (3) 1 & 4 (4) 2 & 4

I
Ans. (2)
4. If the volume of closed vessel in which the following simple reaction is carried out is reduced to one third of original
volume, the rate of reaction becomes

Ans.
5.
2NO(g) + O2 (g)  2NO2 (g)
(1) One third

O
(3) Nine times
(4) S (2) Three times
(4) Twenty seven times

For the reaction A + B  Products, it is found that order of A is 2 and the order of B is 3 in the rate expression. When

O
the concentration of both A and B are doubled the rate will increase by a factor
(1) 10 (2) 16 (3) 32 (4) 28

T
Ans. (3)
6. Nitric oxide (NO) reacts with oxygen to produce nitrogen dioxide

E
2NO(g) + O2 (g)  2NO2 (g), If the mechanism of reaction is
K K1
NO + O2 NO3 (fast), NO3 + NO   NO2 + NO2 (slow) then rate law is
(1) Rate = K’[NO][O2] (2) Rate = K’[NO][O2]2
(3) Rate = K’[NO]2[O2] (4) Rate = K’[NO]3[O2]
Ans. (3)

1
7. For a first order reaction, the time taken to reduce the initial concentration to a factor of is 10 minute. If the
4

1
reduction in concentration is carried out to a factor of , then time required will be
16
(1) 10 minutes (2) 20 minutes (3) 40 minutes (4) 60 minutes
Ans. (2)

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8. For the reaction,

1 d[N 2O5 ]
N 2 O5 
 2NO2  O2 . Given :   K1[N 2 O5 ]
2 dt

d[NO 2 ] d[O 2 ]
 K 2 [N 2O5 ] and  K 3[N 2O5 ]
dt dt
The relation between K1, K2 and K3 is
(1) 2K1 = K2 = 4K3 (2) K1 = K2 = K3 (3) 2K1 = 4K2 = K3 (4) K1 = 2K2 = 3K3
Ans. (1)
K1

A
9. For the reaction, N2O4 (g) 2NO2 (g), the rate of disappearance of NO2 will be
K2

I
(1) K1[N2O4] – K2[NO2]2 (2) 2K1[N2O4] – 2K2[NO2]2
(3) K2[NO2]2 – K1[N2O4] (4) 2K2[NO2]2 – 2K1[N2O4]

D
Ans. (4)
10. For a homogeneous gaseous reaction A  B + C + D, the initial pressure was P0 while pressure after time ‘t’ was P
if (P > P0). The expression for the rate constant K is

(1) K 
2.303
t
 2P0 
log  
 3P0  P 

I(2) K 
2.303
t

N  3P0 
log  
 2P0  P 

Ans.
11.
(3) K 

(1)

O
2.303
t
 P 
log  0 
 P0  P 

S (4) K 
2.303
t
 2P0 
log 

For a gaseous phase reaction 2A + B2  2AB, the following rate date was obtained at 300K

 4P0  P 

O
Rate of disappearance concentration of B2 (mole/litre min)
[A] [B2]

T
(i) 1.8 × 10–3 0.015 0.15
–2
(ii) 1.08 × 10 0.09 0.15
–3

E
(iii) 5.4 × 10 0.015 0.45
The rate constant for the reaction is
(1) 0.5 mol–1 min–1 litre (2) 0.8 mol–1 min–1 litre
(3) 1.5 mol–1 min–1 litre (4) 2 mol–1 min–1 litre
Ans. (2)
12. Inversion of a sugar follows first order rate equation which can be followed by noting the change in rotation of the
plane of polarization of light in the polarimeter. If r, rt and r0 are the rotations at t = , t = t and t = 0 then, first order
reaction can be written as

1 r1  r 1 r0  r 1 r  r0 1 r  rt
(1) K  2 log e r  r (2) K  t ln r  r (3) K  t ln r  r (4) K  t ln r  r
0  t  t   0

Ans. (2)

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13. Which of the following correct ?

K2 E a  T 
(1) log K  2.303  T T 
1  1 2

(2) For zero order t1/2 is inversely proportional to initial concentration

(3) Catalyst decreases the activation energy
(4) All of these
Ans. (3)
14. The rate constant of a reaction is 1.5 × 107 s–1 at 50°C and 4.5 × 107 s–1 at 100°C. What is the value of activation
energy?

A
(1) 2.2 × 103 J mol–1 (2) 2300 J mol–1 (3) 2.2 × 104 J mol–1 (4) 220 J mol–1

I
Ans. (3)
15. In Arrhenius equation, k  Ae  Ea /RT , A may not be termed as rate constant
(1) When 100% reactant will convert into the product

D
(2) When the temperature becomes infinite
(3) When the fraction of molecule crossing over the energy barrier becomes unity

N
(4) At very low temperature

I
Ans. (4)
16. The rate constant of the production of 2B(g) by the reaction,

S

A(g)   2B(g) is 2.48 × 10–4 s–1
A 1:1 molar ratio of A to B in the reaction mixture is attained after
(1) 26.25 minute (2) 27.25 minute (3) 28.25 minute (4) 0 minute

O
Ans. (2)
17. Two substances A and B are present such that [A]0 = 4[B]0 and half life of A is 5 minute and that of B is 15 minute.
If they start decaying at the same time following first order kinetics how much time will the concentration of both of

O
them would be the same ?
(1) 15 minute (2) 10 minute (3) 5 minute (4) 12 minute

T
Ans. (1)
18. If the rate of reaction increases by 27 times, when temperature is increased by 30 K, then temperature coefficient of
the reaction is

E
(1) 3 (2) 2 (3) 1 (4) 2.5
Ans. (1)
19. The reaction A  B follows first order kinetics. The time taken for 0.80 mole of A to produce 0.60 mole of B is 1 hour.
What is the time taken for conversion of 0.90 mole of A to produce 0.675 mole of B ?
(1) 1 hour (2) 30 min (3) 15 min (4) 5 min
Ans. (1)

K1 = 2 × 103 s-1
B
20. If, A
K2 = 6 × 103 s-1
C

find B%
(1) 25% (2) 50% (3) 75% (4) 80%
Ans. (1)

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21. For a first order reaction :–

(1) The degree of dissociation is equal to (1–e–KT)
(2) The preexponential factor in the arrhenius equation has the dimension of time–1
(3) A plot of reciprocal concentration of the reaction v/s time gives a straight line
(4) 1 & 2 both
Ans. (4)

22. Azo isopropane decomposes according to the equation :–

0
250  290 C
(CH3)2CHN = NCH(CH3)2 (g)   N2(g) + C6H14(g)
It is found to be a first order reaction. If initial pressure is Po and pressure of the mixture at time t is (Pt) then

A
rate constant K would be :–

(1) K =

(3) K =
2 .3 0 3

2.303
t
t

o
Po
log P  P
t
Po
log 2 P  P
o t
(2) K =

(4) K =
2 .3 0 3

2.303
t
t

D
2 Po
Po  Pt
log P

log 2 P  P
o t
o

I
N
Ans. (1)

23. Arrhenius equation may be written as :–

(1)

(3)
d
d
dT
(n K) = –

(n K) = +
Ea
RT
Ea
RT 2
S I
(2)

(4)
d
d
dT
(n K) = –

(n K) =
Ea
Ea
RT 2

O
dT dT RT
Ans. (3)

24. A reagent undergoes 90% decomposition in 366 min. According to first order reaction. It's half life is :–

O
 n 2   n 2  1
(1) 366 x 100   (2) 366   (3) (4) 183
 90   n 1 0  366

T
Ans. (2)
25. Which of the following statement is flase :-

E
(1) A fast reaction has a larger rate constant and short half life
(2) For a first order reaction, succession half lives are equal
(3) For a first order reaction, the half life is independent of concentration
(4) The half life of a reaction is half the time required for the reaction to go to completion
Ans. (4)
26. The reaction
CH3COOC2H5 + NaOH CH3COONa + C2H5OH is :-
(1) Bimolecular reaction (2) II order reaction (3) Both (1) & (2) (4) None
Ans. (3)
27. Correct expression for the first order reaction is:-

C C
k1 t k1 t 0 t
(1) Ct = C0 e (2) Ct e = C0 (3) n C = – k1 t (4) n C = k1 t
t 0
Ans. (2)

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28. In a first order reaction, the concentration of the reactant, decreases from 0.8 M to 0.4 M in
15 minutes. The time taken for the concentration to change from 0.1 M to 0.025 M is
(1) 7.5 min (2) 15 min (3) 30 min (4) 60 min
Ans. (3)
29. 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
(1) rate of formation of C is twice the rate of disappearance of A.
(2) Half life is a constant
(3) unit of k must be s–1
(4) value of k is independent of the initial concentrations of A and B

A
Ans. (4)

I
30. The half-life of a radio isotope is four hours. If the initial mass of the isotope was 200 g, the mass remaining
after 24 hours undecayed is :
(1) 3.125 g (2) 2.084 g (3) 1.042 g (4) 4.167 g

D
Ans. (1)
31. For the reaction A + 2B Product, the differential rate equation is :-

N
1 d[A]  d[B] 1 d[A] d[B]
 K[A][B]2  K[A][B]2

I
(1)   (2) 
2 dt dt 2 dt dt

 d[A] 1 d[B] dA 1 d[B]

  K[A][B]2   K[A][B]2

S
(3) (4)
dt 2 dt dt 2 dt
Ans. (3)
32. The t1/2 of a reaction is halved as the initial concentration of the reactant is doubled. What is the order of reaction?

O
(1) First order (2) Zero order (3) Second order (4) Third order
Ans. (3)
33. The rate of a chemical reaction doubles for every 10°C rise of temperature. If the temperature is raised by 50°C,

O
the rate of the reaction increases by about :-
(1) 32 times (2) 64 times (3) 10 times (4) 24 times

T
Ans. (1)
34. A reactant (A) forms two products :
k

E
A 
1
 B, Activation Energy Ea1
k
A  2
 C, Activation Energy Ea2
If Ea2 = 2 Ea1, then k1 and k2 are related as :-
Ea1 / RT
(1) k1 = 2k 2 e Ea 2 / RT (2) k2 = k1e Ea1 / RT (3) k2 = k1e Ea2 / RT (4) k1 = k 2 e
Ans. (4)
35. For a first order reaction, (A)  products, the concentration of A changes from 0.1 M to 0.025M in 40 minutes.
The rate of reaction when the concentration of A is 0.01 M is :-
(1) 1.73 × 10–4 M/min (2) 1.73 × 10–5 M/min (3) 3.47 × 10–4 M/min (4) 3.47 × 10–5 M/min
Ans. (3)

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ASSERTION & REASON EXERCISE

These questions consist of two statements each, printed as Assertion and Reason. While answering these
Questions you are required to choose any one of the following four responses.

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are False.
1. Assertion : The rate of the reaction is the rate of change of concentration of a reactant or a product.
Reason : Rate of reaction remains constant during the complete reaction.
Ans. (C)

A
2. Assertion : The reaction having low value of activation energy are generally fast.

I
Reason : Temperature coefficient for reaction having low activation energy is large.
Ans. (C)
3. Assertion : Half life period is always independent of initial concentration.

D
Reason : Half life period is directly preportional to rate concentration.
Ans. (D)
4. Assertion : The molecularity of a reaction is a whole number other than zero, but generally less then 3.

N
Reason : The order of a reaction is always whole number

I
Ans. (C)
5. Assertion : In a reversible endothermic reaction activation energy of the forward reaction is higher than that
of the backward reaction.

S
Reason : The threshold energy of the forward reaction is more than that of the backward reaction.
Ans. (C)
6. Assertion : The molecularity of the reaction H2 + Br2 2HBr is 2 :

O
3
Reason : The order of the reaction is
2
Ans. (B)

O
7. Assertion : Acid catalysed of ethyl acetate is a first order reaction.
Reason : Water does not take part in the reaction.

T
Ans. (C)
8. Assertion : For a first order reaction t1/2 is independent of the inital concentration of reactants.

E
Reason : For a first order reaction t1/2 is twice the t34.
Ans. (B)
9. Assertion : If in a zero order reaction, the concentration of the reactant is doubled, the half-life period is also
doubled.

Reason : For a zero order reaction, the rate of reaction is independent of initial concentration.
Ans. (B)
10. Assertion : Formation of HI is a biomolecular reaction.

Reason : Two molecules of reactants are involved in this reaction.

Ans. (A)
11. Assertion :- In a first order reaction the rate constant double on doubling the initial concentration of the reaction.
[AIIMS 2010]

Reason :- The rate constant varies directly with the concentration of the reactants in a first order reaction.
Ans. (D)

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12. Assertion :- Two different reaction can never have same rate of reaction [AIIMS 2011]

Reason :- Rate of reaction always depends only on frequency of collision and Arrhenious factor
Ans. (D)
13. Assertion :- Rate of reaction double when concentration of reactant is double if it is a first order reaction.
Reason :- Rate constant also double. [AIIMS 2012]

Ans. (C)
14. Assertion :- The order of a reaction can have fractional value. [AIIMS - 2008]
Reason :- The order of a reaction cannot be written from balanced equation of a reaction.
Ans. (B)
15. Assertion :- Average life of a radioactive element is that period in which 63% of it is decayed. [AIIMS - 2007]

A
Reason :- Average life :  = 1.44t1/2

I
Ans. (B)
16. Assertion :- The hydrolysis of methyl acetate by dil. HCl is a pseudo first order reaction. [AIIMS - 2007]

D
Reason :- HCl acts as a catalyst for the hydrolysis.
Ans. (B)

I N
O S
TO
E
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