Chemistry 12 · Chemistry · Lesson 2.2
Le Châtelier's principle
- Level
- Grade 12
- Reading time
- 11 min reading
- Review
- Last reviewed 2026-09-03
- Standard
- Accuracy standard
- Errata
Abstract
Predicting how a disturbed equilibrium shifts.
What is Le Châtelier’s principle?
Short answer
Le Châtelier’s principle states that if a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, the equilibrium shifts in the direction that partly counteracts the change. Adding a reactant shifts it toward products; increasing pressure shifts it toward the side with fewer gas molecules; raising temperature favours the endothermic direction.
Concept preview
What you will be able to do
- 01State Le Châtelier's principle
- 02Predict the shift caused by a concentration change
- 03Explain a shift using rates and using the reaction quotient Q
Once a system has reached equilibrium, what happens if you disturb it — add a reactant, remove a product, squeeze the container? In 1888 the French chemist Henri Le Châtelier gave a rule that predicts the outcome every time. Le Châtelier's principle states that if a system at equilibrium is subjected to a change in conditions, the equilibrium will shift in the direction that partly counteracts the change, until a new equilibrium is established.
School Plan
Le Châtelier's principle
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Related topics
Frequently asked questions
- How does adding a reactant affect equilibrium?
- The equilibrium shifts toward the products to consume some of the added reactant and partly offset the change.
- Does a catalyst shift the equilibrium?
- No. A catalyst speeds up both directions equally, so it reaches equilibrium faster but does not change its position.