Formula NH4Br Density 2.43 g/cm³ | Molar mass 97.94 g/mol Appearance white powder, hygroscopic | |
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Ammonium bromide, NH4Br, is the ammonium salt of hydrobromic acid. The chemical crystallizes in colorless prisms, possessing a saline taste; it sublimes on heating and is easily soluble in water. On exposure to air it gradually assumes a yellow color because of the oxidation of traces of bromide (Br−) to bromine (Br2).
Contents
Preparation
Ammonium bromide can be prepared by the direct action of hydrogen bromide on ammonia.
NH3 + HBr → NH4Br
It can also be prepared by the reaction of ammonia with iron(II) bromide or iron(III) bromide, which may be obtained by passing aqueous bromine solution over iron filings.
2 NH3 + FeBr2 + 2 H2O → 2 NH4Br + Fe(OH)2Reactions
Ammonium bromide is a weak acid with a pKa of ~5 in water. It is an acid salt because the ammonium ion hydrolyzes slightly in water.
Ammonium Bromide is strong electrolyte when put in water.:
NH4Br(s) → NH4+(aq) + Br−(aq)Ammonium bromide decomposes to ammonia and hydrogen bromide when heated at elevated temperatures:
NH4Br → NH3 + HBrUses
Ammonium bromide is used for photography in films, plates and papers; in fireproofing of wood; in lithography and process engraving; in corrosion inhibitors; and in pharmaceutical preparations.