Hydrochloric Acid
Definition and meaning of Hydrochloric Acid in chemistry.
Hydrochloric acid is a strongly acidic, colorless aqueous system containing hydrogen chloride dissolved in water. It is a highly corrosive, strong mineral acid with many industrial uses and is a primary component of gastric acid in the digestive systems of most animal species. Hydrochloric acid completely dissociates in water into hydronium and chloride ions.
In more detail
The acid is produced industrially by dissolving hydrogen chloride gas in water, often as a co-product of the industrial scale production of other chemicals like chlorinated and fluorinated organic compounds. As a strong acid, it has a high acid dissociation constant and reacts violently with bases, metals, and metal oxides to form chloride salts and, in the case of metals, hydrogen gas. Hydrochloric acid is extensively used for the pickling of steel, a process that removes rust and iron oxide scale from metal surfaces before subsequent processing. It is also utilized in the production of organic compounds such as vinyl chloride and dichloroethane for PVC production, as well as in the synthesis of inorganic compounds like water treatment chemicals. In analytical chemistry, it serves as a standard titrant for determining the concentration of bases in solutions. Despite its highly corrosive nature, it is safely secreted by parietal cells in the human stomach to denature proteins and facilitate digestion.
Key facts
| Field | Inorganic Chemistry |
|---|---|
| Formula | HCl |
| Molar mass | 36.46 g/mol |
| State | Aqueous solution |
| Boiling point | 108.6 °C (20.2% solution) |
When hydrochloric acid is poured over zinc metal, a single displacement reaction occurs, generating zinc chloride and bubbles of hydrogen gas.
Frequently asked questions
What happens when hydrochloric acid is neutralized?
Reacting hydrochloric acid with a base like sodium hydroxide yields water and a salt, such as sodium chloride, in an exothermic neutralization reaction.
How does hydrochloric acid aid digestion?
In the stomach, the acid lowers the pH to around 1.5 to 2.0, which unfolds dietary proteins and activates the digestive enzyme pepsin.