Science · Class 12
Chemical Kinetics
Learn Chemical Kinetics with notes, examples, and practice questions.
3 sections15–25 min read6 MCQs · 2 examples
Chapter Overview
Chemical kinetics studies rate of reactions and factors affecting them — concentration, temperature, catalysts — and integrated rate laws for order determination.
Rate Laws
Rate
Rate = k[A]^m[B]^n
Zero order
[A] = [A]₀ − kt
First order
ln[A] = ln[A]₀ − kt ; t₁/₂ = 0.693/k
Arrhenius
k = Ae^(−E_a/RT)
Factors
- Concentration: more collisions
- Temperature: Arrhenius — more molecules exceed E_a
- Catalyst: lowers E_a, not consumed
- Surface area for heterogeneous reactions
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
First order half-life
k=0.693 hr⁻¹.
- 1t₁/₂=1 hr
Answer
1 hour
Rate
Rate=k[A]², [A] doubles.
- 1Rate increases 4×
Answer
4 times faster
Key Points to Remember
- ✓ Order from experiment, not equation
- ✓ Molecularity for elementary steps
- ✓ Rate-determining step in mechanism
Exam Tips
- • Plot ln[A] vs t for first order straight line
- • Units of k depend on order
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Formula Cheat Sheet
Quick reference — NCERT board exam formulas
Rate Laws
- Rate:Rate = k[A]^m[B]^n
- Zero order:[A] = [A]₀ − kt
- First order:ln[A] = ln[A]₀ − kt
- Half-life (1st order):t₁/₂ = 0.693/k
- Arrhenius:k = Ae^(−E_a/RT)
Practice MCQs — Chemical Kinetics
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 6Score: 0/0
First order t₁/₂ =