Chapter 2 of 15
Revision Notes
Ionic Equilibrium — Revision Notes
Tamil Nadu Board · Class 12 · Chemistry
Ionic Equilibrium revision notes for Tamil Nadu Board Class 12 Chemistry: 4 topics in quick points. Includes Acid-Base Theories, Ionisation of Water.
45 questions30 flashcards7 formulas & key relations5 concepts
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Key Topics to Revise
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1. Acid-Base Theories
- Three major theories explain acid-base behaviour: Arrhenius, Bronsted-Lowry, and Lewis.
- Arrhenius concept is the most limited; it only works in aqueous solutions.
- Bronsted-Lowry theory introduced the concept of conjugate acid-base pairs.
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2. Ionisation of Water and pH Scale
- Pure water undergoes self-ionisation (auto-ionisation): H₂O + H₂O ⇌ H₃O⁺ + OH⁻
- Ionic product of water Kw = [H₃O⁺][OH⁻] = 1 × 10⁻¹⁴ at 25°C
- Since water ionisation is endothermic, Kw increases with temperature.
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3. Ionisation of Weak Acids and Bases – Ostwald's Dilution Law
- Weak acids and bases are only partially dissociated in water — an equilibrium exists between dissociated ions and undissociated molecules.
- The dissociation constant Ka (for acids) and Kb (for bases) measure the strength of weak electrolytes.
- Higher Ka means stronger acid; higher Kb means stronger base.
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4. Common Ion Effect
- When a salt having a common ion with a weak electrolyte is added to the solution of the weak electrolyte, the degree of dissociation of the weak electrolyte decreases — this is the Common Ion Effect.
- Example: Adding CH₃COONa (which gives CH₃COO⁻) to CH₃COOH suppresses the dissociation of acetic acid.
- CH₃COONa → Na⁺ + CH₃COO⁻ (complete dissociation of salt)
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Full NotesKey Concepts
According to Svante ArrheniusA more general definition whereAn acid accepts an electron pairPure water undergoes autopH =
Frequently Asked Questions
What are the important topics in Ionic Equilibrium for Tamil Nadu Board Class 12 Chemistry?
Key topics in Ionic Equilibrium include Acid-Base Theories, Ionisation of Water and pH Scale, Ionisation of Weak Acids and Bases – Ostwald's Dilution Law, Common Ion Effect. Study these first, then practise questions on each for the Tamil Nadu Board Class 12 board exam.
How should I revise Ionic Equilibrium for the Tamil Nadu Board Class 12 board exam?
Learn the core ideas first, then work through the 45 practice questions on Ionic Equilibrium. Revise definitions regularly and use flashcards for quick recall before the exam.
Sources & Official References
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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