Carbonic acid is a weak acid that is created when carbon dioxide (CO2) is dissolved in water (H2O), resulting in the chemical formula H2CO3. When the acid dissociates, or gives up a hydrogen ion, the resulting molecule is called a bicarbonate ion. Carbonic acid appears frequently in the natural world. It can be found in sodas, champagne, and blood. The acid even appears in rain.
During the making of soda, carbon dioxide is dissolved in water. As stated, this process also creates carbonic acid. This acid, along with phosphoric acid and other acids, provides the tart taste in many sodas. It also provides a slight burning sensation that a person feels when ingesting a fizzy drink. Thus, it is the carbonic acid that makes fizzy drinks taste fizzy.
Carbonic acid plays an important role in keeping the body’s pH stable. The normal pH of bodily fluids is around 7.4 and must be kept close to this value in order for the body to function properly. If the pH changes, whether up or down, enzymes can stop functioning, muscles and nerves can start weakening, and metabolic activities becomes impaired. The bicarbonate ion released from carbonic acid serves as a buffer that helps resist changes in pH. This means it can act as an acid or a base as the need arises.