Le Chatelier's principle, also called Chatelier's principle, is a principle of chemistry used to predict the effect of a change in conditions on chemical equilibrium. The principle is named after French chemist Henry Louis Le Chatelier, and sometimes also credited to Karl Ferdinand Braun, who discovered it independently. It can be defined as:If the equilibrium of a system is disturbed by a change in one or more of the determining factors the system tends to adjust itself to a new equilibrium by counteracting as far as possible the effect of the change
The reversible reaction N2O4(g) ⇌ 2NO2(g) is endothermic, so the equilibrium position can be shifted by changing the temperature. When heat is added and the temperature increases, the reaction shifts to the right and the flask turns reddish brown due to an increase in NO2. This demonstrates Le Chatelier's principle: the equilibrium shifts in the direction that consumes energy. When heat is removed and the temperature decreases, the reaction shifts to the left and the flask turns colorless due to an increase in N
Henry Louis Le Chatelier was a French chemist of the late 19th and early 20th centuries. He devised Le Chatelier's principle, used by chemists and chemical engineers to predict the effect a changing condition has on a system in chemical equilibrium.
The Sorbonne. Professor Henry Louis Le Chatelier (Bibliothèque de La Sorbonne, NuBIS)
