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Chapter 2 of 15
Revision Notes

Ionic Equilibrium

Tamil Nadu Board · Class 12 · Chemistry

Quick revision notes for Ionic Equilibrium — Tamil Nadu Board Class 12 Chemistry. Key concepts, formulas, and definitions for last-minute revision.

45 questions30 flashcards5 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 Notes

Key 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 Ionic Equilibrium – Complete Chapter Overview, Ionic Equilibrium - Concepts Hierarchy, Overview of Ionic Equilibrium - Key Topics. These are the concepts Tamil Nadu Board Class 12 examiners draw on most — study them first, then practise related questions.
How to score full marks in Ionic Equilibrium — Tamil Nadu Board Class 12 Chemistry?
Understand the core concepts first, then work through the 45 practice questions available for this chapter. Revise formulas and 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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