2KBr

2KBr is not a distinct chemical compound. In chemical notation, it represents two formula units of potassium bromide, KBr. Potassium bromide is an ionic salt composed of potassium cations (K+) and bromide anions (Br−) arranged in a crystal lattice. The term 2KBr often appears only as a stoichiometric coefficient in balanced equations, for example in the synthesis of potassium bromide from elements: 2K + Br2 → 2KBr.

Physical and chemical properties

Potassium bromide (KBr) is a white, crystalline solid at room temperature. It has a high melting point and is readily soluble in water. In solid form it adopts a rock-salt type lattice structure typical of many alkali metal halides.

Preparation

Potassium bromide can be prepared by neutralizing hydrobromic acid with potassium hydroxide: HBr + KOH → KBr + H2O. It can also be produced by direct reaction of elemental potassium with bromine: 2K + Br2 → 2KBr, a method that demonstrates its formation from the elements.

Uses and applications

Historically, potassium bromide was used as a sedative and anticonvulsant in medicine. In the laboratory, KBr serves as a source of bromide ion and as a reagent in various organic synthesis procedures. It has also been used in early photography due to its role in bromide-based gelatin emulsions; modern photographic practices have largely moved away from this use.

Safety

Potassium bromide is of relatively low acute toxicity compared with many other inorganic salts, but excessive exposure or ingestion can lead to bromide accumulation (bromism) and other health effects. Proper handling and storage are advised, particularly to avoid ingestion by children and pets.

See also: Potassium bromide.