Monoprotic Acid Definition

Nitric acid
A monoprotic acid, such as nitric acid (shown here), donates one hydrogen or proton. Laguna Design / Getty Images

Monoprotic Acid Definition

A monoprotic acid is an acid that donates only one proton or hydrogen atom per molecule to an aqueous solution. This is in contrast to acids capable of donating more than one proton or hydrogen, which are called polyprotic acids. Polyprotic acids may be further categorized according to how many protons they can donate (diprotic = 2, triprotic = 3, etc.).

The electrical charge of a monoprotic acid is one level higher before it gives away its proton. Any acid that one contains one hydrogen atom in its formula is monoprotic. However, some acids that contain more than one hydrogen atom are monoprotic. Because only one hydrogen is released, the pH calculation for a monoprotic acid is straightforward.

A monoprotic base will only accept a single hydrogen atom or proton.

Monoprotic Acid Examples

Hydrochloric acid (HCl) and nitric acid (HNO3) are both monoprotic acids. Although it contains more than one hydrogen atom, acetic acid (CH3COOH) is also a monoprotic acid, as it only dissociates to release a single proton.

Examples of Polyprotic Acids

Here are some examples of polyprotic acids.

Diprotic acids:
                              1. Sulfuric acid, H2SO4
                              2. Carbonic acid, H2CO3
                              3. Oxalic acid, COOH-COOH

Triprotic acids:   
                              1. Phosphoric acid, H3PO4
                              2. Arsenic acid, H3AsO4
                              3. Citric acid, CH2COOH-C(OH)(COOH)-CH2COOH