Equilibrium
Chemical Equilibrium · Ionic Equilibrium · pH · Buffers · Solubility Product · Le Chatelier Principle · Complete Coverage
Equilibrium Key Topics
Master reversible reactions, equilibrium constants, Le Chatelier principle, ionic equilibrium, pH calculations and buffer solutions for JEE Main Chemistry.
Chemical Equilibrium
Reversible reactions, dynamic equilibrium, Kc, Kp and reaction quotient.
Le Chatelier Principle
Effect of concentration, pressure, volume and temperature on equilibrium.
Ionic Equilibrium
Weak acids, weak bases, ionization constants and degree of dissociation.
pH & Buffers
pH, pOH, buffer solutions, Henderson equation and salt hydrolysis.
Solubility Product
Ksp, common ion effect, solubility and precipitation conditions.
Applications
Use equilibrium concepts in numerical problems and chemical processes.
Essential Equations & Relations
Important formulas for equilibrium constants, pH calculations and buffer solutions.
- Kc = [C]^c[D]^d / [A]^a[B]^b
- Kp = Kc(RT)^Δn
- ΔG° = −RT ln K
- Q < K: forward reaction favoured
- Q > K: reverse reaction favoured
- Q = K: equilibrium
- pH = −log[H⁺]
- pOH = −log[OH⁻]
- pH + pOH = 14 at 25°C
- [H⁺] weak acid = √(Ka × C)
- [OH⁻] weak base = √(Kb × C)
- pH = pKa + log([Salt]/[Acid])
Chemical & Ionic Equilibrium
Build a strong foundation before attempting JEE Main numerical problems.
- Reversible reactions
- Dynamic equilibrium
- Equilibrium constant
- Reaction quotient
- Le Chatelier principle
- Temperature and pressure effects
- Weak acids and bases
- Ka, Kb and Kw
- pH and pOH calculations
- Buffer solutions
- Salt hydrolysis
- Ksp and common ion effect
Le Chatelier Principle
Predict the direction of equilibrium shift when conditions change.
| Change | Equilibrium Shift | Key Point | Remark |
|---|---|---|---|
| Reactant increases | Towards products | Forward shift | Consumes added reactant |
| Product increases | Towards reactants | Reverse shift | Consumes added product |
| Pressure increases | Fewer gas moles | Depends on Δn | Only gaseous systems |
| Temperature increases | Endothermic direction | Depends on ΔH | Catalyst does not shift equilibrium |
| Best Practice | The system opposes the applied change to restore equilibrium. | ||
How to Master Equilibrium?
Follow this practical sequence for JEE Main Chemistry preparation.
Learn Kc & Kp
Understand equilibrium expressions, reaction quotient and relation between Kc and Kp.
Apply Le Chatelier
Practise concentration, pressure and temperature based shift questions.
Practise pH
Study weak acids, weak bases, Ka, Kb and approximation methods.
Revise Buffers & Ksp
Master Henderson equation, salt hydrolysis, solubility and precipitation.
Complete Chapter Breakdown
All important Equilibrium topics for JEE Main Chemistry.
Chemical Equilibrium
- Reversible Reactions
- Kc & Kp
- Reaction Quotient
- Le Chatelier
- Temperature Effect
- Pressure Effect
- Catalyst Effect
Ionic Equilibrium
- Weak Acids
- Weak Bases
- Ka & Kb
- pH Calculations
- Common Ion Effect
- Hydrolysis
- Indicators
Buffers & Ksp
- Buffer Solutions
- Henderson Equation
- Acidic Buffers
- Basic Buffers
- Solubility Product
- Precipitation
- Applications
Key Constants to Remember
Useful values and relations for JEE Main calculations.
Gas Constant
R = 0.0821 L atm K⁻¹ mol⁻¹ or 8.314 J K⁻¹ mol⁻¹.
Water Ionisation
Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25°C; pH + pOH = 14.
Gibbs Relation
ΔG° = −RT ln K. K > 1 generally indicates product-favoured equilibrium.
Log Relations
pKa = −log Ka, pKb = −log Kb and [H⁺] = 10⁻pH.
JEE Main Question Patterns
Common Equilibrium questions and their standard approach.
| Question Type | Typical Approach | Difficulty | Remark |
|---|---|---|---|
| Kc/Kp calculation | Write equilibrium expression | Easy-Moderate | Check gaseous moles |
| Le Chatelier | Predict shift direction | Easy | Identify applied change |
| pH calculation | Use Ka, Kb or Kw | Moderate | Check approximation |
| Buffer solution | Use Henderson equation | Moderate | Identify acid/salt ratio |
| Best Strategy | Practise ICE tables, logarithms and approximation-based numerical questions. | ||
Frequently Asked Questions
Common questions about Equilibrium for JEE Main Chemistry.
Chemical equilibrium is the dynamic state in which forward and reverse reaction rates are equal. Concentrations remain constant, although both reactions continue.
When an equilibrium system is disturbed, it shifts in the direction that opposes the change and helps restore equilibrium.
pH = −log[H⁺]. At 25°C, pH 7 is neutral, pH below 7 is acidic and pH above 7 is basic.
A buffer resists change in pH and usually contains a weak acid with its salt or a weak base with its salt.
No. A catalyst speeds up both forward and reverse reactions equally, so it changes the time needed to reach equilibrium but not the equilibrium position.
Equilibrium is an important Physical Chemistry chapter. Prepare both conceptual questions and numerical problems from chemical and ionic equilibrium.
Master Equilibrium Now
Revise formulas, practise numerical problems and test your JEE Main Chemistry preparation.