Introduction: All around us are acids and bases. The oranges and lemons that we eat contain a specific acid known as citric acid. Our soap contains a small amount of a base known as sodium hydroxide. But, what exactly are acids and bases? This is where the definitions of acids and bases based on Svante Arrhenius' definitions come in.

Svante Arrhenius defined Arrhenius acids as substances that dissociated in aqueous solution to produce [math]"H"^"+"[/math], or hydrogen ions, as the only positive ions. One example of an Arrhenius acid is HCl. It is worth noting that hydrogen ions typically do not exist in aqueous solution on their own, however. Instead, hydrogen ions typically combine with water in aqueous solution to form a hydronium ion, written as [math]"H"_3"O"^"+"[/math]. Arrhenius acids tend to turn litmus red and tend to neutralize bases.

Svante Arrhenius defined Arrhenius bases as substance that dissociated in aqueous solution to produce [math]"OH"^"-"[/math], or hydroxide ions, as the only negative ions. One example of an Arrhenius base is NaOH. Arrhenius bases tend to turn litmus blue and tend to neutralize acids.