Main Page | See live article | Alphabetical index

Common-ion effect

Certain molecules dissociate completely into two ions when placed into water- for example, NaCl dissociates into Na+ and Cl-. When such a salt is added to a chemical reaction that involves an ion common to one of those formed by the dissociation of a salt, Le Chatelier's principle comes into play, and the reaction may be driven in one direction or another.