súra

Sýra is the Icelandic word for acid. In chemistry, acids are substances that in aqueous solution increase the concentration of hydrogen ions (H+) and can donate protons to other substances, according to Arrhenius and Bronsted–Lowry theories. Modern understanding also includes Lewis acids, which accept electron pairs. Acids can be inorganic or organic and vary widely in strength, reactivity, and appearance, but many share characteristic reactions such as turning blue litmus red.

Inorganic acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), and phosphoric acid (H3PO4). Organic acids include acetic acid (CH3COOH), citric acid (C6H8O7), and formic acid (HCOOH). Strong acids dissociate completely in water, while weak acids dissociate only partially; strength is quantified by the acid dissociation constant (Ka) or pKa values.

Common properties of acids include a pH below 7 in aqueous solution, a historical association with sour taste, and corrosiveness. They react with metals to release hydrogen gas and with carbonates to form carbon dioxide. Acids conduct electricity when dissolved, due to the mobility of ions.

Uses and safety: Acids are essential in chemical synthesis, digestion (gastric acid in the stomach), cleaning and metal pretreatment, pH control in agriculture and industry, and food additives. They require careful handling, proper storage, ventilation, and protective equipment due to their corrosive nature.

History and theory: The Arrhenius definition emerged in the 19th century, with Bronsted and Lowry broadening the concept in the 1920s and Lewis contributing an additional framework. The Icelandic term sýra aligns with these scientific concepts and is used for acids in chemistry and related fields.