Editing Le Chatelier's principle (section)

===Effect of change in concentration===
Changing the concentration of a chemical will shift the equilibrium to the side that would counter that change in concentration. The chemical system will attempt to partly oppose the change that affected the original state of equilibrium. In turn, the rate of reaction, extent, and yield of products will be altered corresponding to the impact on the system.

This can be illustrated by the equilibrium of [[carbon monoxide]] and [[hydrogen]] gas, reacting to form [[methanol]]. 

:[[Carbon|C]][[Oxygen|O]] + 2 H<sub>2</sub> ⇌ CH<sub>3</sub>OH

Suppose we were to increase the concentration of CO in the system. Using Le Chatelier's principle, we can predict that the concentration of methanol will increase, decreasing the total change in CO. If we are to add a species to the overall reaction, the reaction will favor the side opposing the addition of the species. Likewise, the subtraction of a species would cause the reaction to "fill the gap" and favor the side where the species was reduced. This observation is supported by the [[collision theory]]. As the concentration of CO is increased, the frequency of successful collisions of that reactant would increase also, allowing for an increase in forward reaction, and generation of the product. Even if the desired product is not [[thermodynamic]]ally favored, the end-product can be obtained if it is continuously removed from the [[Solution (chemistry)|solution]].

The effect of a change in concentration is often exploited synthetically for [[condensation reaction]]s (i.e., reactions that extrude water) that are equilibrium processes (e.g., the formation of an [[ester]] from carboxylic acid and alcohol or an [[imine]] from an amine and aldehyde).  This can be achieved by physically sequestering water, by adding desiccants like anhydrous magnesium sulfate or [[molecular sieve]]s, or by continuous removal of water by distillation, often facilitated by a [[Dean–Stark apparatus|Dean-Stark apparatus]].