àcids

Àcids is the Catalan term for acids, a class of chemical compounds notable for their ability to donate protons or produce hydrogen ions in solution. In the Brønsted–Lowry framework, acids are substances that donate protons (H+), while bases accept them. In the Arrhenius sense, acids are substances that increase the concentration of H+ (as hydronium, H3O+) in water. A broader perspective uses the Lewis definition, where acids are electron-pair acceptors. These definitions together describe the diverse behavior of acids in chemical reactions.

Acids are commonly classified as inorganic or organic. Inorganic acids include well-known examples such as hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), and phosphoric acid (H3PO4). Organic acids primarily feature acidic hydrogen attached to carbonyl-bearing groups, with carboxylic acids like acetic acid (CH3COOH), formic acid (HCOOH), and citric acid among the most important. Many acids show varying strength; strong acids dissociate completely in water, while weak acids only partially dissociate, a property described by their acid dissociation constant (Ka) and pKa values.

Common properties of acids include a sour taste, the ability to turn blue litmus red, and corrosivity. They react with metals to produce hydrogen gas and with carbonates to release carbon dioxide. Uses span from laboratory reagents and catalysts in organic synthesis to digestion in biological systems, such as gastric hydrochloric acid.

Safety and handling focus on preventing skin and eye contact, controlling fumes, and proper storage due to corrosive and reactive nature.

See also: pH, acid strength, conjugate acid-base pairs, proton donor, carboxylic acids.