Class 12 Chemical Kinetics Numericals CBSE | Important Formulas, Solved Problems & Exam Guide
Table of Contents
Chemical Kinetics Numericals – Class 12 CBSE Complete Exam Guide
Chemical Kinetics is one of the most important and high-scoring chapters in Class 12 Chemistry CBSE.
This chapter contains direct numericals in board exams, and if you learn formulas properly, you can easily score full marks.
Chemical kinetics deals with rate of reactions, factors affecting rate, and mathematical expressions for reactions.
High Weightage Topics in Chemical Kinetics (CBSE)
These topics are frequently asked in exams:
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Rate of Reaction
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Rate Law and Order of Reaction
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Integrated Rate Equations
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Half-life of Reactions
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Arrhenius Equation
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Collision Theory
Tip: Numericals mostly come from order of reaction and half-life formulas.
Important Formulas for Chemical Kinetics (Must Memorize)
| Topic | Formula |
|---|---|
| Rate Law | Rate = k[A]^m[B]^n |
| Zero Order Half-life | t₁/₂ = [A]₀ / 2k |
| First Order Half-life | t₁/₂ = 0.693 / k |
| First Order Rate Constant | k = 2.303/t × log([A]₀/[A]) |
| Arrhenius Equation | k = Ae^(-Ea/RT) |
| Arrhenius (log form) | log k = log A − Ea / (2.303RT) |
These formulas are very important for CBSE numericals.
Important Chemical Kinetics Numericals with Solutions
Numerical 1: First Order Reaction
Question:
The rate constant (k) of a first-order reaction is 0.693 min⁻¹. Find the half-life.
Solution:
Formula:
t₁/₂ = 0.693 / k
t₁/₂ = 0.693 / 0.693 = 1 minute
Numerical 2: Zero Order Reaction
Question:
A zero-order reaction has k = 2 mol L⁻¹ s⁻¹ and initial concentration = 10 mol L⁻¹. Find half-life.
Solution:
t₁/₂ = [A]₀ / 2k
= 10 / (2 × 2)
= 2.5 seconds
Numerical 3: First Order Rate Constant
Question:
If initial concentration is 1 M and after 10 min it becomes 0.25 M, find k.
Solution:
k = 2.303/t × log([A]₀/[A])
= 2.303/10 × log(1/0.25)
= 0.2303 × log 4
= 0.138 min⁻¹ (approx)
Numerical 4: Arrhenius Equation
Question:
Calculate Ea if k1 and k2 are given at two temperatures.
Formula:
log(k2/k1) = Ea / 2.303R × (1/T1 − 1/T2)
This type of numerical is frequently asked in CBSE exams.
Order of Reaction Quick Revision Table
| Order | Half-life Dependence | Graph |
|---|---|---|
| Zero Order | Depends on initial concentration | Straight line |
| First Order | Independent of initial concentration | Exponential curve |
| Second Order | Depends on initial concentration | Curve |
Easy-to-Score Topics in Chemical Kinetics
These topics give direct marks:
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Definitions (Rate, Order, Molecularity)
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Half-life formulas
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Arrhenius equation
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Difference between order and molecularity
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Graphs of zero and first order reactions
Memorizing formulas can help you solve numericals easily.
Exam Tips for Chemical Kinetics Numericals
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Learn all formulas by heart
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Practice at least 5 numericals daily
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Write formula first in exam
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Show proper steps (marks are given for steps)
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Learn graphs and theory questions too
Chemical Kinetics is one of the most scoring chapters in Physical Chemistry.
Conclusion
Chemical Kinetics numericals are easy and scoring in Class 12 Chemistry CBSE. By learning formulas, practicing basic problems, and understanding graphs, students can easily score full marks. Focus on half-life, rate constant, and Arrhenius equation numericals for maximum marks.
Click here to read about Class 12 D and F Block Important Questions 2026 | CBSE Chemistry High Weightage Topics: https://dekhocampus.com/news/class-12-d-and-f-block-important-questions-2026-cbse
FAQs (Frequently Asked Questions)
Half-life, rate constant, order of reaction, and Arrhenius equation numericals are most important.
No, it is easy if you memorize formulas and practice questions.
Usually around 4–7 marks in board exams.
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