Le Chatelier's principle (synopsis)
A 2004 concentration-focused synopsis of Le Chatelier’s principle (neglecting temperature, pressure, and volume change factors) by American organic chemists Marye Fox and James Whitesell. [5]
In chemistry, Le Chatelier’s principle, also called "Le Chatelier-Braun principle" (Lindsay, 1927), after Karl Braun, or "principle of mobile equilibrium" or "general law of inertia", is a generalized rule which states that perturbation of a system at equilibrium will cause the equilibrium position to change in such a way as to tend to remove the perturbation. [1] In short, systems in equilibrium tend to react to perturbations in a transformational direction towards the change, thus re-establishing a new equilibrium.


In the early 1880s, French chemist Henry Le Chatelier (1850-1936) was a professor of chemistry at the École des Mines in Paris working on the theoretical and practical aspects of chemistry. His research on the chemistry of cements led him to formulate a principle to predict how changing the pressure affected a chemical system. [2] The new equilibrium principle discerned by Le Chatelier was first published in an 1884 note by him in the following form: [3]

"Any system in stable chemical equilibrium, subjected to the influence of an external cause tends to change either its temperature or its condensation (pressure, concentration, number of molecules in unit volume), either as a whole or in some of its parts, can only undergo such internal modifications as would, if produced alone, bring about a change of temperature or of condensation of opposite sign to that resulting from the external cause."

Four years later, in a longer 1888 article entitled “Experimental and Theoretical Research on Chemical Equilibria” in the Annales des Mines, Le Chatelier restated the Principle in a simpler and more comprehensive form: [4]

“Every change of one of the factors of an equilibrium occasions a rearrangement of the system in such a direction that the factor in question experiences a change in a sense opposite to the original change.”

The expanded paper contains a large number of applications to equilibria including ones involving electromotive force as well as pressure and temperature. The extension of this argument to include applications to biology and social sciences have been made by later writers and were not represented in Le Chatelier's original explanation.

See also
Social Le Chatelier principle

1. Smith, Eric B. (2005). Basic Chemical Thermodynamics (pg. 61). Imperial College Press.
2. Myers, Richard. (2003). The Basics of Chemistry (pg. 149). Greenwood Publishing Group.
3. Le Chatelier, Henry. (1884). “Title”, Comptes rendus, 99, 786.
4. (a) Le Chatelier, Henry. (1888). “Title”, Annales des Mines, 13 (2), 157.
(b) Le Chatelier, H. (1888). “Recherches Experimentales et Theoriques sur les Equilibres Chimiques (Experimental and Theoretical Research on Chemical Equilibria).” Annales des Mines, Hutieme Serie, Memiories, XIII, Paris: Dunod.
5. Fox, Marye A. and Whitesell, James K. (2004). Organic Chemistry (pg. 322). Jones & Barlett Learning.

Further reading
● Oliver, John and Kurtz, Jim. (c.2000). “Henry Louis Le Chatelier: A Man of Principle”, Woodrow.org.

External links
Le Chatelier’s principle – Wikipedia.

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