Chemical Species

With these models and the equations in examples 12 and 13 you have seen how we represent the different forms in which chemicals can exist as they dissolve and possibly dissociate. We have a special name for each part or form in which a chemical exists when it is dissolved in solution. We call these chemical species.

Let's refer back to some of the chemicals shown in example 12. When NaCl dissolves in water we don't really have any NaCl as such in the solution. We have Na⁺ and Cl^- ions because NaCl dissociates. We say the species present in solution are Na⁺(aq) and Cl^-(aq). The same is true for any strong electrolyte--the species present in solution are the ions.

For a nonelectrolyte, like C₂H₅OH, which does not dissociate into ions the specie present is the same as before it was put into solution except that it is surrounded by water molecules. Nonelectrolytes have molecular species in solution unlike strong electrolytes which have ionic species in solution.

Weak electrolytes have both molecular and ionic species present in solution because some of the molecules dissociate into ions and some do not. Usually the molecular species are present in much greater numbers than the ionic species because only a small percentage of the molecules in a weak electrolyte actually dissociate.

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E-mail instructor: Eden Francis

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