Le Chatelier's Principle

Le Chatelier's principle [lə′shäd·əl‚yāz ‚prin·sə·pəl]

(physics)

The principle that when an external force is applied to a system at equilibrium, the system adjusts so as to minimize the effect of the applied force.

---

Le Châtelier’s Principle 

(known in Russian as Le Châtelier-Braun principle), a principle stating that an external influence causing a shift in the thermodynamic equilibrium of a system brings about processes in the system tending to counteract the effect of that influence. Thus, the heating of a system in equilibrium produces internal changes (for example, chemical reactions) that are accompanied by heat absorption, and the cooling of a given system produces changes that are accompanied by the evolvement of heat. The shift in equilibrium under increased pressure is connected with a reduction in the overall volume of a system; a decrease in pressure is accompanied by physical or chemical processes leading to an increase in volume.

In 1884, J. Van’t Hoff formulated the principle of shift in equilibrium as a function of temperature. The given principle was generalized by H. Le Châtelier in 1884, and C. Braun gave his thermodynamical substantiation in 1887. Le Châtelier’s principle was formulated by analogy with the Lenz law of induction; the principle is rigorously derived from the general condition of thermodynamic equilibrium (maximum entropy). Le Châtelier’s principle makes it possible to determine the direction of the shift in equilibrium of a thermodynamic system without a detailed analysis of the equilibrium conditions.