Phosphoric acid
This equation shows that the pH of a solution of a weak acid depends on both its formula_1 value and its concentration. Typical examples of weak acids include acetic acid and phosphorous acid. An acid such as oxalic acid (&lt;chem&gt;HOOC-COOH&lt;/chem&gt;) is said to be dibasic because it can lose two protons and react with two molecules of a simple base. Phosphoric acid (&lt;chem&gt;H3PO4&lt;/chem&gt;) is tribasic.