Class 11 Chemistry Chapter 6 Equilibrium – Revision Notes

Equilibrium is defined here as the point where forward and reverse reaction rates become equal, expressed through the equilibrium constant K_c and shifted, according to Le Chatelier’s principle, by changes in concentration, pressure, or temperature. The chapter also covers acid-base theories, pH calculations, and how buffers resist changes in pH.

Last Updated: September 23, 2026

Equilibrium Basics

• Dynamic equilibrium: forward rate=reverse rate.
• K_c=[products]/[reactants] (each raised to stoichiometric coefficient).

Le Chatelier’s Principle

• Equilibrium shifts to counteract imposed change (concentration, pressure, temperature).

Acids, Bases, pH

• Arrhenius, Brønsted-Lowry, Lewis definitions.
• pH=−log[H⁺]; K_w=10⁻¹⁴ at 25°C.

Buffers

• Resist pH change; weak acid/base + conjugate; common ion effect.

One-Line Summary

Equilibrium describes the dynamic balance between forward and reverse reactions, governed by the equilibrium constant and Le Chatelier’s principle, extending to acid-base and buffer systems in solution.

Frequently Asked Questions

What does it mean for a chemical reaction to be at equilibrium?
A reaction is at equilibrium when the rate of the forward reaction equals the rate of the reverse reaction, so the concentrations of reactants and products remain constant over time, even though both reactions continue to occur.

How does Le Chatelier Principle predict the effect of changing conditions on equilibrium?
Le Chatelier Principle states that if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the equilibrium shifts in the direction that tends to counteract that change.

Written by Satish

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