M.C.Q : Chemical Kinetics ( 11 to 2 0 )

LEVEL – I
11. If a reaction with t1/2 = 69.3 sec , has a rate constant 10–2 sec–1 , the order is

(A) 0

(B) 1

(C) 2

(D) 3

12. The specific rate constant for a first order reaction is 60 × 10–4 sec–1. If the initial concentration of the reactant is 0.01 mol L—1 , the rate is

(A) 60 × 10<sup–6< sup=”” m=”” sec<sup=””>—1

(B) 36 × 10<sup–4< sup=”” m=”” sec<sup=””>—1

(C) 60 × 10<sup–2< sup=”” m=”” sec<sup=””>—1

(D) 36 × 10<sup–1< sup=”” m=”” sec<sup=””>—1

13. The rate constant 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 have been

(A) 0.5 M

(B) 1.25 M

(C) 12.5 M

(D) 1.0 M

14. A first order reaction is carried out with an initial concentration of 10 ML–1 and 80% of the reactant changes into the product. Now if the same reaction is carried out with an initial concentration of 5 ML–1, the percentage of reactant changing to the product is

(A) 40

(B) 80

(C) 160

(D) can’t be calculated

15. What fraction of a reactant showing first order remains after 40 min , if t1/2 is 20 min ?

(A) 1/4

(B) 1/2

(C) 1/8

(D) 1/6

16. A substance undergoes a first order decomposition. The decomposition follows two parallel first order reaction as

The percentage distribution of B and C are

(A) 80% B and 20% C

(B) 75% B and 25% C

(C) 90% B and 10% C

(D) 60% B and 40% C

17. A tangent drawn on the curve obtained by plotting concentration of product (mole L–1) of a first order reaction vs. time (min) at the point corresponding to time 20 minute makes an angle to 30° with concentration axis. Hence the rate of formations of product after 20 minutes will be

(A) 0.580 mole L–1 min–1

(B) 1.723 mole L–1 mi–1–1

(C) 0.290 mole L–1 min–1

(D) 0.866 mole L–1 min–1

18. For reaction 3A −> products, it is found that the rate of reaction increases 4 – fold when concentration of A is increased 16 times keeping the temperature constant. The order of reaction is ?

(A) 2

(B) 1

(C) 1

(D) 0.5

19. The thermal decomposition of acetaldehyde : CH3CHO −> CH4 + CO , has rate constant
of 1.8 × 10–3 mole–1/2 L1/2 min–1 at a given temperature.

How would will change if concentration of acetaldehyde is doubled keeping the temperature constant ?

(A) will increase by 2.828 times

(B) will increase by 11.313 times

(C) will not change

(D) will increase by 4 times

20. The reaction ; 2O3 −> 3O2 , is assigned the following mechanism.
(I) O3 <−> O3 + O
(II) O3 + O −>(slow) 2O2
The rate law of if the reaction will, therefore be

(A) r ∝ [O3]2[O2]

(B) r ∝ [O3]2 [O2]–1

(C) r ∝ [O3]

(D) r ∝ [O3] [O2]–2

ANSWER:

11. B   12. A   13. A   14. B   15. D   16. B   17. B   18. D   19. A   20. D

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M.C.Q : Chemical Kinetics ( 21 to 30 )

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