Chemistry · Class 11 · Equilibrium

Ionic Equilibrium (pH, Buffers, Ksp) for JEE

Everything you need for this topic on one page: the ideas, the formulas, the traps, and free lectures that explain it well.

Last updated: 26 October 2026

Direct answer

Acids and bases, pH, weak acid dissociation, salt hydrolysis, buffers, solubility product and common ion effect.

Key ideas

Ionic Equilibrium (pH, Buffers, Ksp): what you must understand

pH + pOH = 14 at 25 °C
Buffers resist pH change; Henderson equation gives their pH
Common ion lowers solubility
Precipitation happens when ionic product > Ksp

Formula sheet

Must-know formulas for Ionic Equilibrium (pH, Buffers, Ksp)

Weak acid: [H⁺] = √(Ka C)
Henderson: pH = pKa + log([salt]/[acid])
Ksp for AB₂: 4s³
Salt of weak acid + strong base: pH = 7 + ½(pKa + log C)

One-page formula sheet

Printable Ionic Equilibrium (pH, Buffers, Ksp) formula sheet: formulas, key ideas and traps on one page. Save it as a PDF for offline revision.

Avoid

Common mistakes students make

Using the strong-acid formula for weak acids
Forgetting dilution when two solutions are mixed
Wrong Ksp expression for the formula

For the exam

How this topic is asked in JEE

Appears frequently. Buffer and Ksp numericals appear regularly. Learn the standard pH formulas as a table.

Prerequisites: Chemical Equilibrium.

NCERT map

Where Ionic Equilibrium (pH, Buffers, Ksp) is in NCERT

Chapter names follow the current rationalised NCERT textbooks. Read these sections before solving PYQs.

Class	Book	Chapter	Sections JEE asks from
Class 11	Chemistry Part I	Equilibrium	Ionization of Acids and Bases; Buffer Solutions; Solubility Equilibria of Sparingly Soluble Salts; Common Ion Effect; Ionization of Water and pH Scale

JEE Advanced level

A JEE Advanced-level example on Ionic Equilibrium (pH, Buffers, Ksp)

Question. A buffer solution is prepared by mixing 100 mL of 0.2 M CH₃COOH with 100 mL of 0.1 M NaOH. Solid AgCH₃COO is added to this buffer until saturation. Given Ka of CH₃COOH = 2 × 10⁻⁵ and Ksp of AgCH₃COO = 2 × 10⁻³, find the concentration of Ag⁺ ions in the saturated solution.

Show solution

Moles of CH₃COOH = 0.02 mol, moles of NaOH = 0.01 mol. NaOH neutralizes equal moles of acid, so after reaction: CH₃COOH = 0.01 mol, CH₃COO⁻ = 0.01 mol in 200 mL total volume.
Concentration of acetate ion in buffer: [CH₃COO⁻] = 0.01 mol / 0.2 L = 0.05 M. This acts as the common ion.
When AgCH₃COO dissolves: AgCH₃COO ⇌ Ag⁺ + CH₃COO⁻. At saturation, Ksp = [Ag⁺][CH₃COO⁻].
Apply common ion effect. The buffer maintains [CH₃COO⁻] ≈ 0.05 M since Ag⁺ dissolved is small compared to buffer capacity.
[Ag⁺] = Ksp / [CH₃COO⁻] = (2 × 10⁻³) / (0.05) = 4 × 10⁻² M

Answer: [Ag⁺] = 4 × 10⁻² M (or 0.04 M)

This example was solved twice independently and both solutions agree.

Free lectures

Best free lectures for Ionic Equilibrium (pH, Buffers, Ksp)

Full-chapter free lectures picked from YouTube search results by views, from established JEE channels (mostly in Hinglish). Use the subtopic list to jump straight to the part you need (timestamps come from each video's own chapter list). Watch one, then solve PYQs the same day.

IONIC EQUILIBRIUM in One Shot - Full Chapter Revision | Class 11 | JEE Main — JEE Wallah, 2:24:15
Jump to a subtopic (26)
- 0:00 Introduction
- 2:30 Types of electrolytes
- 5:17 Arrhenius theory
- 6:18 Bronsted theory
- 7:50 Lewis theory
- 9:16 Conjugate acid and base
- 11:49 Amphiprotic species
- 12:57 pH calculation
- 23:36 pH Numerical
- 28:05 pH of weak mono basic acids and mono acidic bases
- 32:14 pH Numerical
- 33:19 pH of weak poly basic acids and poly acidic bases
- 35:50 pH Numerical
- 36:39 pH of mixture of weak acids and weak bases
- 38:15 pH Numerical
- 41:06 pH of Mixture of strong acid/base with weak acid/base
- 45:33 pH of Amphiprotic Species
- 47:03 Some Important Points
- 47:35 Salt Hydrolysis
- 1:2:57 Buffer Solution
- 1:16:54 Calculation of pH when weak acid + strong base mixing
- 1:27:22 Solubility and Solubility product
- 1:32:58 Solubility in common ion effect
- 1:38:24 Ionic Product of Salt
- 1:43:50 PYQs
- 2:23:15 Thank You
Ionic Equilibrium FULL CHAPTER | Class 11th Physical Chemistry | Chapter 6 | Arjuna JEE — Arjuna JEE, 4:30:01
Jump to a subtopic (17)
- 00:00 Introduction
- 03:29 Electrolytes and Non Electrolytes
- 07:57 Acids and Bases
- 08:23 Arrhenius Concept
- 11:13 The Bronsted - lowry Concept
- 19:01 Lewis Concept
- 30:00 Ionic Product of Water
- 42:40 The pH Scale
- 54:44 Ionization Constants of Weak Acids
- 01:07:08 Ionization Constants of Weak Bases
- 01:11:55 Relationship Between Ka and Kb
- 01:15:47 Common Ion Effect
- 02:28:25 Salt Hydrolysis
- 02:57:58 Buffer Solutions
- 03:42:39 Solubility Equilibria
- 04:07:14 Common Ion Effect
- 04:26:47 Thank You Bachoo!!

Practise

Where to practise for free

1 JEE Main 2026 PYQs on Ionic Equilibrium (pH, Buffers, Ksp), with solutions.
Read the chapter in NCERT textbooks (official, free), then solve its NCERT Exemplar (official, free) questions.
Chapter-wise past questions: JEE Main and Advanced PYQs and question bank.
Timed practice tests: NTA Abhyas practice tests (official, free) and our free mock tests.
See it move: interactive simulation.

FAQs

Frequently asked questions

Is Ionic Equilibrium (pH, Buffers, Ksp) important for JEE Main 2027?

Appears frequently. It is part of the official 'Equilibrium' unit in the JEE Main 2027 syllabus.

What are the most important formulas in Ionic Equilibrium (pH, Buffers, Ksp)?

Weak acid: [H⁺] = √(Ka C); Henderson: pH = pKa + log([salt]/[acid]); Ksp for AB₂: 4s³.

How should I study Ionic Equilibrium (pH, Buffers, Ksp) for JEE?

Understand the key ideas from NCERT or one full lecture, learn the formula sheet, then solve 25–30 past JEE questions on the topic. Buffer and Ksp numericals appear regularly. Learn the standard pH formulas as a table.