halogeenihapon

Halogeenihapon is the Finnish term for a hydrohalic acid. These are binary compounds of hydrogen and a halogen. The halogens are fluorine, chlorine, bromine, iodine, and astatine. Therefore, the six hydrohalic acids are hydrogen fluoride (HF), hydrogen chloride (HCl), hydrogen bromide (HBr), hydrogen iodide (HI), and hydrogen astatide (HAt). In aqueous solution, these compounds are acids. Hydrochloric acid (HCl in water), hydrobromic acid (HBr in water), and hydroiodic acid (HI in water) are strong acids. Hydrogen fluoride (HF in water) is a weak acid. Hydrogen astatide (HAt) is highly unstable and radioactive, and its acidic properties are not well-studied.

Hydrohalic acids are formed when hydrogen halides react with water. For example, hydrogen chloride gas dissolves in water to form hydrochloric acid. These acids are corrosive and have various industrial and laboratory applications. Hydrochloric acid is used in steel pickling, chemical synthesis, and pH regulation. Hydrofluoric acid is used in etching glass and in the production of refrigerants and plastics. Hydrogen bromide and hydrogen iodide are used in organic synthesis and as reducing agents. The stability of the hydrogen-halogen bond decreases down the group, with HF being the strongest and HI being the weakest. This trend influences the strength of the corresponding acids in aqueous solution, with HF being the weakest due to strong hydrogen bonding and the high electronegativity of fluorine, which polarizes the O-H bond in water more effectively.