common-ion effect definition of common-ion effect in the Free Online Encyclopedia.

common-ion effect, decrease in solubility of an ionic salt salt, chemical compound (other than water) formed by a chemical reaction between an acid and a base (see acids and bases ).

Characteristics and Classification of Salts

..... Click the link for more information. , i.e., one that dissociates in solution into its ions ion, atom or group of atoms having a net electric charge .

Positive and Negative Electric Charges

A neutral atom or group of atoms becomes an ion by gaining or losing one or more electrons or protons.
..... Click the link for more information. , caused by the presence in solution solution, in chemistry, homogeneous mixture of two or more substances. The dissolving medium is called the solvent , and the dissolved material is called the solute. A solution is distinct from a colloid or a suspension .
..... Click the link for more information. of another solute that contains one of the same ions as the salt. The common-ion effect is an example of chemical equilibrium chemical equilibrium, state of balance in which two opposing reversible chemical reactions proceed at constant equal rates with no net change in the system. For example, when hydrogen gas, H₂, and iodine gas, I₂
..... Click the link for more information. . For example, silver chloride, AgCl, is a slightly soluble salt that in solution dissociates into the ions Ag⁺ and Cl⁻, the equilibrium state being represented by the equation AgCl_solid[right pointing harpoon over left pointing harpoon]Ag⁺+Cl⁻. According to Le Châtelier's principle Le Châtelier's principle, chemical principle that states that if a system in equilibrium is disturbed by changes in determining factors, such as temperature, pressure, and concentration of components, the system will tend to shift its equilibrium position so as
..... Click the link for more information. , when a stress is placed on a system in equilibrium, the system responds by tending to reduce that stress. In the system taken as an example, if another solute containing one of those ions is added, e.g., sodium chloride, NaCl, which supplies Cl⁻ ions, the solubility equilibrium of the solution will be shifted to remove more Cl⁻ from the solution, so that at the new equilibrium point there will be fewer Ag⁺ ions in solution and more AgCl precipitated out as a solid.