Silver bromide Formula

Silver bromide Formula

Silver bromide, also known as bromargyrite or bromyrite, is an inorganic salt very useful to produce photographic materials such as films.

Formula and structure: Silver bromide chemical formula is AgBr and the molar mass is 187.77 g mol-1. The molecule is formed by the cation Ag1+ and the anion bromide Br1- and the structure is similar to the salt sodium chloride NaCl with a face-centered cubic lattice structure and where 1 ion is surrounded by 6 opposite charged ions. Its chemical structure can be written as below, in the common representations used for organic molecules.

Occurrence: Silver bromide can be found in nature as being part of the geological formations and in the mineral bromargyrite.

Preparation: In general, silver bromide is prepared using a reaction between silver nitrate and sodium or potassium bromide (a mixture is performed in aqueous solution):

AgNO3 + KBr → AgBr(s)+ K+ + NO3-

AgNO3 + KBr → AgBr(s)+ K+ + NO3-

Physical properties: Silver bromide is a pale-yellow soft solid or powder. Its density is 6.473 g mL-1 and its melting and boiling points are 432ºC and 700ºC. Up to 700ºC it decomposes. It is insoluble in water and is photosensitive.

Chemical properties: Silver bromide can be used in synthesis to form amine complexes owing its capacity to react easily with ammonia. Some of the complexes can be produced are:

AgBr + nNH3 → [Ag(NH3)2]+

AgBr + nNH3 → [Ag(NH3)2]

AgBr + nNH3 → [Ag(NH3)]

AgBr + NH3 → [Ag(NH3)]-

Silver bromide is a photosensitive substance, thus it can produce a determinate reaction when are received photons from a light source. This property allows the use of silver bromide in photographic supplies and is based in the removal of one electron by the action of a photon which incident over the material:

X- + hν → X + e-

Uses: Silver bromide is largely used to produce photographic supplies, film and photochemical. AgBr is also used in organometallic synthesis to form amine complex such as described above. Moreover, silver bromide is used as semiconductor to produce electronic devices.

Health effects / safety hazards: Silver bromide is very toxic to animals and is very dangerous to the aquatic environment. It is not flammable.

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