# Chapter 4 Chemical Kinetics MCQs for Class 12 Chemistry

#### Chapter 4 Chemical Kinetics MCQs for Class 12 Chemistry

Here students can practice Chapter 4 Chemical Kinetics MCQs for Class 12 Chemistry. All the MCQs are divided into several sub-pages. Each page has 40 MCQs, for the next page just scroll down and click on the button. Also you can practice Class 12 Chemistry MCQs (Multiple Choice Questions) for other units.

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Q 1.: The rate of reaction increases with increase in temperature, because _______

(A) Activation energy increases

(B) Threshold energy increases

(C) The number of molecules undergoing effective collision increases

(D) Energy barrier decreases

Option – C

Q 2.: Which of the following statements is incorrect regarding order of reaction and molecularity ?

(A) Molecularity is the theoretical conclusion while order of reaction is experimental conclusion

(B) Molecularity explains the reaction mechanism while reaction order does not give any information about reaction mechanism

(C) The value of molecularity is positive integer while the value of reaction order may be positive and zero

(D) For elementary reactions, the order of reaction and molecularity are same

Option – B

Q 3.: When the rate of the reaction is equal to the rate constant, the order of the reaction is

(A) Zero order

(B) First order

(C) Second order

(D) Third order

Option – A

Q 4.: What is indicated by  $$-\frac{1}{2}\frac{d[N_{2}O_{5}]}{dt}$$  ?

(A) Order of reaction

(B) Rate law expression

(C) Decomposition rate of N2O5

(D) Rate of formation of N2O5

Option – C

Q 5.: In a reaction, 2A → B, the concentration of A decreases from 0.50 M to 0.38 M in 10 min. What is the rate of reaction in molL-1s-1 during this interval ?

(A) 2 × 10-4

(B) 4 × 10-2

(C) 2 × 10-2

(D) 1 × 10-2

Option – A

Q 6.: In a reaction, A + B → Product, rate is doubled when the concentration of B is doubled, and rate increases by a factor of 8 when the concentration of both the reactants (A and B) are doubled. Rate law expression for the reaction can be written as

(A) Rate = k [A][B]2

(B) Rate = k [A]2[B]2

(C) Rate = k [A][B]

(D) Rate = k [A]2[B]

Option – D

Q 7.: For the reaction, N2 + 3H2  →  2NH3 , if  $$\frac{d[NH_{3}]}{dt}$$ = 2 × 10–4 mol L–1 sec–1 , the value of  $$-~\frac{d[H_{2}]}{dt}$$ would be

(A) 3 × 10–4 mol L–1 sec–1

(B) 4 × 10–4 mol L–1 sec–1

(C) 6 × 10–4 mol L–1 sec–1

(D) 1 × 10–4 mol L–1 sec–1

Option – A

Q 8.: The reaction 2NO (g) + O2 (g)  ⇄  2NO2 (g) is of first order. If volume of reaction vessel is reduced to 1/3 the rate of reaction would be

(A)  $$\frac{1}{3}$$ times

(B)  $$\frac{2}{3}$$ times

(C) 3 times

(D) 6 times

Option – C

Q 9.: A gaseous hypothetical chemical equation 2A 4B + C is carried out in a close vessel. The concentration of ‘B’ is found to increase by 5 × 10–3 mol L–1 sec–1 in 10 sec. The rate of appearance of ‘B’ is

(A) 5 × 10–4 mol L–1 sec–1

(B) 5 × 10–5 mol L–1 sec–1

(C) 6 × 10–5 mol L–1 sec–1

(D) 4 × 10–4 mol L–1 sec–1

Option – A

Q 10.: The rate constant for the reaction, 2N2O5  →  4NO2 + O2 , is 3.0 × 10–5 sec–1. If the rate is 2.40 × 10–5 mol L–1 sec–1, then concentration of N2O5 (in mol L–1) is

(A) 1.4

(B) 1.2

(C) 0.04

(D) 0.8

Option – D

Q 11.: In the reaction,

$$BrO_{3}^{-}+5Br_{}^{-}+H^{+}~\rightarrow ~3Br_{2}+3H_{2}O$$,

The rate of appearance of bromine (Br2) is related to rate of disappearance of the bromide ions as following

(A)  $$\frac{d[Br_{2}]}{dt}~=~-\frac{3}{5}\frac{d[Br^{-}]}{dt}$$

(B)  $$\frac{d[Br_{2}]}{dt}~=~-\frac{5}{3}\frac{d[Br^{-}]}{dt}$$

(C)  $$\frac{d[Br_{2}]}{dt}~=~\frac{5}{3}\frac{d[Br^{-}]}{dt}$$

(D)  $$\frac{d[Br_{2}]}{dt}~=~\frac{3}{5}\frac{d[Br^{-}]}{dt}$$

Option – A

Q 12.: The reaction follows the mechanism

$$A~+~B~\xrightarrow[]{~~k_{1}~~}~AB~~~~(fast)$$

$$AB~+~B~\xrightarrow[]{~~k_{2}~~}~A~+~B_{2}~~~~(slow)$$

then rate law is

(A) rate = k[A][B]

(B) rate = k[AB][B]

(C) rate = k[A][B]2

(D) rate = k[A]2[B]

Option – B

Q 13.: For a reaction, the dimensions of rate constant are same as that of rate, hence order of reaction is

(A) Zero

(B) First

(C) Second

(D) Third

Option – A

Q 14.: Half life period for a first order reaction is 10 min. Starting with 10 M, the rate after 20 min is

(A) 0.0693 M min–1

(B) 0.0693 × 5 M min–1

(C) 0.0693 × 2.5 M min–1

(D) 0.0693 × 10 M min–1

Option – C

Q 15.: For a reaction, A + B → Product, it is observed that

I.  On doubling the initial concentration of A only, the rate of reaction is also doubled

II. On doubling the initial concentration of both A and B, there is a change by a factor 8 in the rate of reaction.

The rate of reaction is given by

(A) rate = k[A]2[B]

(B) rate = k[A][B]2

(C) rate = k[A]2[B]2

(D) rate = k[A][B]

Option – B

Q 16.: The half-life of a reaction inversely proportional to the square of the initial concentration of the reactant. Then, the order of reaction is

(A) Zero

(B) First

(C) Second

(D) Third

Option – D

Q 17.: For a first order reaction, the time taken to reduce the initial concentration by a factor of 1/4 is 20 min. The time required to reduce initial concentration by a factor of 1/16 is

(A) 10

(B) 20

(C) 40

(D) 80

Option – C

Q 18.: Which of the following is the correct statement ?

(A) Order of a reaction has always an integral value

(B) Mechanism of a reaction proposed is always final

(C) Zero order reactions are multi-step reactions

(D) Order of reaction can be predicted even without knowing the rate law

Option – D

Q 19.: For the reaction n1A + n2B → Products; rate =K[A]3[B]0 if concentration of A is doubled and concentration of B is halved, then reaction rate __

(A) Is doubled

(B) Increased by four times

(C) Increased by six times

(D) Increased by eight times

Option – D

Q 20.: According to law of mass action rate of a chemical reaction is proportional to

(A) Concentration of reactants

(B) Molar concentration of reactants

(C) Concentration of products

(D) Molar concentration of products

Option – B

Q 21.: If the relation between half-life period of a reaction and initial concentration of reactants [R]0 , is  $$t_{\frac{1}{2}}\propto \frac{1}{[R]_{0}^{n-1}}$$ , then what will be the order of reaction ?

(A) n – 1

(B) n

(C)  $$\frac{n-2}{2}$$

(D)  $$\frac{1}{n-2}$$

Option – B

Q 22.: The rate law for the reaction , xA + yB  → mP + nQ , is rate = k[A]c[B]d. What is the total order of the reaction ?

(A) (x + y)

(B) (m + n)

(C) (c + d)

(D) (2x + y)

Option – C

Q 23.: If two reactants are taking part in the reaction, then the reaction will never be

(A) Mono-molecular

(B) First order

(C) Bi-molecular

(D) Second order

Option – A

Q 24.: Of which of the following factors, the rate of reaction depends on

(A) Atomic mass of reactant

(B) Equivalent weight of reactant

(C) Active mass of reactant

(D) Atomic mass of product

Option – C

Q 25.: Which one of the following statements for the order of a reaction is incorrect ?

(A) Order of reaction is always whole number

(B) Order can be determined only experimentally

(C) Order is not influenced by stochiometric coefficient of the reactants

(D) Order of reaction is sum of power to the concentration in terms of reactants to express the rate of reaction

Option – A

Q 26.: The fist order integrated rate equation is

(A)  $$k=-\frac{2.303}{t}log\frac{a}{a-2x}$$

(B)  $$k=\frac{1}{t}log\frac{x}{a(a-x)}$$

(C)  $$k=-\frac{2.303}{t}log\frac{a}{a-x}$$

(D)  $$k=\frac{1}{t}ln\frac{a}{a-x}$$

Option – D

Q 27.: The thermal decomposition of a molecule shows first order kinetics. The molecule decomposes 50% in 120 min. How much time it will take to decompose 90% ?

(A) 360 min

(B) 398.8 min

(C) 402.5 min

(D) 407 min

Option – B

Q 28.: The reactions having very high value of activation energy are generally _________

(A) Very slow

(B) Very fast

(C) Spontaneous

(D) None of these

Option – A

Q 29.: The decomposition of N2O5 into NO2 and O2 is first order reaction with rate constant 6.2 × 10–4 sec–1. What is the value of rate of reaction when [N2O5] = 1.25 mol L–1.

(A) 3.85 × 10–4 mol L–1 sec–1

(B) 5.15 × 10–5 mol L–1 sec–1

(C) 6.35 × 10–3 mol L–1 sec–1

(D) 7.75 × 10–4 mol L–1 sec–1

Option – D

Q 30.: The unit of rate constant depends upon

(A) Rate of reaction

(B) Order of reaction

(C) Molecularity of reaction

(D) All of the above

Option – B

Q 31.: For a first order reaction k = 10–3 min–1 , its half-life period is _______

(A) 800 min

(B) 500 min

(C) 600 min

(D) 693 min

Option – D

Q 32.: For which reaction the collision theory is generally more satisfactory ?

(A) Zero order

(B) First order

(C) Second order

(D) Any order

Option – C

Q 33.: Which of the following reaction will be comparatively the slowest ?

(A) Decomposition of urea in presence of urease enzyme

(B) Formation of rust on iron in presence of inhibitors

(C) The combination of N2 and O2 when lightening is there in the sky

(D) The rate of reverse reaction is presence of catalyst

Option – B

Q 34.: What will be the half-life period of a first order reaction with rate constant k = 5.5 × 10–14 sec–1 ?

(A) 1.26 × 1013 sec

(B) 2.16 × 1013 sec

(C) 1.26 × 10–13 sec

(D) 2.16 × 10–13 sec

Option – A

Q 35.: Elementary reaction 2SO2 (g) + O2 (g)  → Product. If pressure is increased by three times, then  reaction rate ___________

(A) Increased by 3 times

(B) Increased by 9 times

(C) Increased by 18 times

(D) Increased by 27 times

Option – D

Q 36.: Which of these does not influence the rate of reaction ?

(A) Nature of the reactants

(B) Concentration of the reactants

(C) Temperature of the reaction

(D) Molecularity of the reaction

Option – D

Q 37.: The inversion of cane sugar is first order and proceeds with half-life of 600 minutes at pH=4 for a given concentration of sugar. However, if pH=5, the half-life changes to 60 minutes, The rate law expression for the sugar inversion can be written as :

(A) rate = k[sugar]1[H+]2

(B) rate = k[sugar]1[H+]1

(C) rate = k[sugar]1[H+]0

(D) rate = k[sugar]2[H+]1

Option – C

Q 38.: On increasing the pressure three-fold, the rate of reaction of 2H2S + O2  → Product , would increase

(A) Increased by 3 times

(B) Increased by 9 times

(C) Increased by 18 times

(D) Increased by 27 times

Option – D

Q 39.: 75% of a first order reaction is completed in 30 minutes, what is the time required for 93.75% of the reaction (in minutes) ?

(A) 40

(B) 60

(C) 80

(D) 90

Option – B

Q 40.: For elementary reaction, which of the following is correct ?

(A) Order of reaction = molecularity

(B) Order of reaction > molecularity

(C) Order of reaction < molecularity

(D) Order of reaction ≠ molecularity

Option – A

Pagination

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We hope that these Chapter 4 Chemical Kinetics MCQs for Class 12 Chemistry helped you in learning new concepts. All questions are based on NCERT syllabus and some of them have been asked in various competitive exams. You can go to the next pages to practice more for Chapter 4 Chemical Kinetics MCQs for Class 12 Chemistry, click on the question range given above.

Also you can practice Class 12 Chemistry MCQs (Multiple Choice Questions) for other units.