Le Chatelier's Principle: Understanding Chemical Equilibrium

Le Chatelier's Principle

Definition and Historical Context

Le Chatelier's principle, also known as the Le Chatelier-Braun principle (LCB principle), is a concept in chemistry that was developed independently by Henri Louis Le Chatelier and Karl Ferdinand Braun in the late 19th century. The principle asserts that when a system in dynamic equilibrium is subjected to an external stress, it will adjust its composition to counteract the stress and establish a new equilibrium. The principle was first introduced in Le Chatelier's treatise, which was published in 1888.

The LCB principle is not a law, but rather a guideline that can be used to predict changes in chemical equilibria when a system is subjected to a disturbance. It complements the laws of chemistry by providing a simple rule of thumb for understanding reflex activity and predicting changes in chemical systems.

Application in Chemistry

Le Chatelier's principle is particularly useful in understanding how chemical systems respond to changes in temperature, pressure, or concentration of reactants or products. When a system at equilibrium is disturbed by changing one of these factors, the position of equilibrium shifts to counteract the change and re-establish equilibrium.

For example, if a system at equilibrium is subjected to an increase in pressure, the reaction will shift to the side with fewer moles of gas to reduce the pressure. A decrease in pressure will cause the reaction to shift in the opposite direction, producing more moles of gas.

Application in Other Scientific Fields

The LCB principle has been extended to other scientific fields, such as physics and psychology. In the field of psychology, it has been suggested that the principle governs the processes of sensation and perception, with a restoring influence acting to mute or turn off stimuli and restore equilibrium. This principle can be applied to advantage in sensory science, where it can help understand the mechanisms behind sensory adaptation and the response of organisms to changes in their environment.

Summary and Conclusions

Le Chatelier's principle is a fundamental concept in chemistry that helps explain how chemical systems respond to external stresses. It is a useful guide for predicting changes in chemical equilibria and has been extended to other scientific fields, such as psychology. The principle is not a law, but rather a rule of thumb that complements the laws of science. It provides a simple way to understand reflex activity and predict changes in chemical systems, but it should be used with caution, as it is an extrapolation of the known laws of chemistry, biochemistry, and biophysics. The incumbency remains to discover these laws in detail, relegating LCB to its proper place as an adjunctive principle.