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Chemical Kinetics Questions and Answers | Chemistry MCQs for Class 12 with Answers Chemical Kinetics

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(1) This reaction follows first order kinetics. The rate constant at particular temperature is 2.303 × 10−2 hour−1 . The initial concentration of cyclopropane is 0.25M. What will be the concentration of cyclopropane after 1806 minutes? (log 2 = 0.3010)
[A] 0.125M
[B] 0.215M
[C] 0.25 × 2.303M
[D] 0.05M
Answer: 0.215M
(2) For a first order reaction, the rate constant is 6.909 min-1.the time taken for 75% conversion in minutes is
[A] (3/2)log2
[B] (2/3)log2
[C] (3/2)log(3/4)
[D] (2/3)log(4/3)
Answer: (2/3)log2

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(3) In a first order reaction x → y ; if k is the rate constant and the initial concentration of the reactant x is 0.1M, then, the half life is

[A] (a)
[B] (b)
[C] (c)
[D] (d)
Answer: (c)
(4) Predict the rate law of the following reaction based on the data given below

2A + B → C + 3D

[A] rate = k [ A]2 [B]
[B] rate = k [ A][B]2
[C] rate = k [ A][B]
[D] rate = k [ A]1/2 [B]3/2
Answer: rate = k [ A][B]2
(5) Assertion: rate of reaction doubles when the concentration of the reactant is doubles if it is a first order reaction.

Reason: rate constant also doubles

[A] Both assertion and reason are true and reason is the correct explanation of assertion.
[B] Both assertion and reason are true but reason is not the correct explanation of assertion.
[C] Assertion is true but reason is false.
[D] Both assertion and reason are false.
Answer: Assertion is true but reason is false.
(6) The rate constant of a reaction is 5.8 × 10−2 s−1 . The order of the reaction is
[A] First order
[B] zero order
[C] Second order
[D] Third order
Answer: First order
(7)

For the reaction  N2O5(g) → 2NO2 (g) + ½ O2(g), the value of rate of disappearance of N2O5 is given as 6.5 × 10-2 mol L-1 s-1. The rate of formation of NO2 and O2 is given  respectively as

[A]

( 3.25 × 10−2 mol L−1s−1 ) and (1.3 × 10−2 mol L−1s−1 )

[B]

(1.3 × 10−2 mol L−1s−1 ) and ( 3.25 × 10−2 mol L−1s−1 )

[C]

(1.3 × 10−1 mol L−1s−1 ) and ( 3.25 × 10−2 mol L−1s−1 )

[D] None of these
Answer:

(1.3 × 10−1 mol L−1s−1 ) and ( 3.25 × 10−2 mol L−1s−1 )

(8) During the decomposition of H2O2 to give dioxygen, 48 g O2 is formed per minute at certain point of time. The rate of formation of water at this point is
[A] 0.75 mol min−1
[B] 1.5 mol min−1
[C] 2.25 mol min−1
[D] 3.0 mol min−1
Answer: 3.0 mol min−1
(9) If the initial concentration of the reactant is doubled, the time for half reaction is also doubled. Then the order of the reaction is
[A] Zero
[B] one
[C] Fraction
[D] none
Answer: Zero
(10) In a homogeneous reaction A →B + C + D , the initial pressure was P0 and after time t it was P. expression for rate constant in terms of P0, P and t will be

[A] (a)
[B] (b)
[C] (c)
[D] (c)
Answer: (a)

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