CBSE Class 12th Chemistry Chapter 3 - Chemical Kinetics Important Questions with Answers

You should focus on solving CBSE Class 12th Chemistry Chapter 3: Chemical Kinetics important questions, especially to help you score high marks. By solving CBSE Class 12th Chemistry 3 questions, you will be solving exam-oriented questions only.

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CBSE Class 12th Chemistry Chapter 3 - Chemical Kinetics includes the following topics: Rate of a reaction (Average and instantaneous), factors affecting rate of reaction: concentration, temperature, catalyst; order and molecularity of a reaction, rate law and specific rate constant, integrated rate equations and half-life (only for zero and first order reactions), concept of collision theory (elementary idea, no mathematical treatment), activation energy, Arrhenius equation. This chapter is included in the fourth unit of the syllabus. The weightage of the chapter will be 7 marks. The theory paper will be conducted for 70 marks. The theory paper will include different types of questions based on the curriculum followed by CBSE. There will be no overall choice in the question paper. However, 33% of internal choices will be given in all the sections.

The Central Board of Secondary Education has already released the latest curriculum on the official website of CBSE Academics. To prepare well for the exam, you must download the latest syllabus PDF from the official website and complete it as soon as possible. After completing your syllabus, you can move forward with the model test papers available on the official website and practice them one by one. After completing the sample question papers, you can also pick up the previous years' question papers uploaded on the official website of CBSE at cbse.nic.in. Since Chemistry is a practical subject, do not forget to also give importance to the practical exam. The practical exam will be conducted for 30 marks. The 30 marks will be divided into different parameters.

For Chemistry, you must make notes after the end of every chapter to revise efficiently. Keep your practical file up to date. Take part in group studies to clear your doubts easily. Take help from YouTube to understand difficult topics.

The Central Board of Secondary Education has already released the date sheet for class 12th, according to which the exams start on 15th February 2025. Given below, we are sharing the CBSE Class 12th Chemistry Chapter 3 - Chemical Kinetics Important Questions with Answers here. Make sure to attempt the questions after completing your syllabus, and you can also check the correct answers by clicking on the tab given below:

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For a reaction R ? P, half-life (t_1/2) is observed to be independent of the initial concentration of reactants. What is the order of reaction? (Delhi 2017)

Question 2.

For a chemical reaction R ? P, variation in ln[R] vs time (f) plot is given below:
For this reaction:
(i) Predict the order of reaction
Important Questions for Class 12 Chemistry Chapter 4 Chemical Kinetics Class 12 Important Questions 11

Important Questions for Class 12 Chemistry Chapter 4 Chemical Kinetics Class 12 Important Questions 11

(ii) What is the unit of rate constant (k)? (Comptt. Delhi 2017)

Question 3.

(a) Explain why H₂ and O₂ do not react at room temperature.
(b) Write the rate equation for the reaction A₂ + 3B₂ ? 2C, if the overall order of the reaction is zero. (Comptt. All India 2017)

Question 4.

Derive integrated rate equation for rate constant of a first order reaction. (Comptt. All India 2017)

Question 5.

(i) What is the order of the reaction whose rate constant has same units as the rate of reaction?
(ii) For a reaction A + H₂O ? B; Rate ? [A],
What is the order of this reaction? (Comptt. All India 2017)

Question 6.

Define rate of reaction. (Comptt. Delhi 2016)

Question 7.

Define rate constant (K). (Comptt. All India 2016)

Question 8.

For a reaction: 2NH₂(g)

\overset{Pt}{⟶}

N₂(g) + 3H₂(g)
Rate = k
(i) Write the order and molecularity of this reaction.
(ii) Write the unit of k. (Delhi 2016)

Question 9.

For a reaction: H₂ + Cl₂

\overset{hv}{⟶}

2HCl
Rate = k
(i) Write the order and molecularity of this reaction.
(ii) Write the unit of k. (All India 2016)

Question 10.

The rate constant for the first order decomposition of H₂O₂ is given by the following equation:
log k = 14.2 –

\frac{1.0 \times 10^{4}}{T} K

Calculate E_a for this reaction and rate constant k if its half-life period be 200 minutes.
(Given: R = 8.314 J K^-1 mol^-1) (Delhi 2016)

Question 1.

For the first order thermal decomposition reaction, the following data were obtained:
C₂H₅Cl(g) ? C₂H₄(g) + HCl(g)
Time/sec Total pressure/atm
0 0.30
300 0.50
Calculate the rate constant (Given: log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021) (All India 2016)

Question 2.

If the half-life period of a first order reaction in A is 2 minutes, how long will it take [A] to reach 25% of its initial concentration? (Comptt. Delhi 2016)

Question 3.

The rates of most reactions double when their temperature is raised from 298 K to 308 K. Calculate their activation energy. [R = 8.314 JK^-1 mol^-1] (Comptt. All India 2016)

Question 4.

Following data are obtained for the reaction:
N₂O₅ ? 2NO₂ +

\frac{1}{2}

O₂(a) Show that it follows first order reaction.
(b) Calculate the half-life.
(Given log 2 = 0.3010 log 4 = 0.6021) (Delhi 2016)

Question 5.

A first order reaction takes 20 minutes for 25% decomposition. Calculate the time when 75% of the reaction will be completed.
(Given: log 2 = 0.3010, log 3 = 0.4771, log 4 = 0.6021) (All India 2016)

Question 6.

The following data were obtained during the first order thermal decomposition of SO₂Cl₂ at a constant volume :Calculate the rate constant (k).
[Given : log 2 = 0.3010; log 4 = 0.6021] (Comptt. Delhi 2016)

Question 7.

For the first order decomposition of azoisopropane to hexane and nitrogen at 543 K , the following data were obtained :
Calculate the rate constant. The equation for the reaction is :(CH₃)₂CHN = NCH(CH₃)₂ C₆H₁₄ (g) + N₂ (g)
[Given : log 3 = 0.4771; log 5 = 0.6990] (Comptt. Delhi 2016)

Question 8.

For a first order reaction, show that time required for 99% completion is twice the time required for completion of 90% reaction. (Comptt. All India 2016)

Question 9.

Half-life for a first order reaction 693 s. Calculate the time required for 90% completion of this reaction. (Comptt. All India 2016)

Question 10.

(a) Explain the following terms :
(i) Order of a reaction
(ii) Molecularity of a reaction
(b) The rate of a reaction increases four times when the temperature changes from 300 K to 320 K. Calculate the energy of activation of the reaction, assuming that it does not change with temperature. (R = 8.314 J K^-1 mol^-1) (All India 2016)