Page "Chemistry" Paragraph 61

A substance can often be classified as an acid or a base.

There are several different theories which explain acid-base behavior.

The simplest is Arrhenius theory, which states than an acid is a substance that produces hydronium ions when it is dissolved in water, and a base is one that produces hydroxide ions when dissolved in water.

According to Brønsted – Lowry acid-base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction ; by extension, a base is the substance which receives that hydrogen ion.