Ammonium bromide

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 bromide (Br⁻) to bromine (Br₂).

Ammonium bromide

ball-and-stick model of an ammonium cation (left) and a bromide anion (right)
Names
IUPAC name Ammonium bromide
Identifiers
CAS Number	12124-97-9 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:85364 N
ChemSpider	23804 Y
ECHA InfoCard	100.031.973
EC Number	235-183-8
PubChem CID	25514
RTECS number	BO9155000liugoiugiu
UNII	R0JB3224WS Y
CompTox Dashboard (EPA)	DTXSID8035681
InChI InChI=1S/BrH.H3N/h1H;1H3 Y Key: SWLVFNYSXGMGBS-UHFFFAOYSA-N Y InChI=1/BrH.H3N/h1H;1H3 Key: SWLVFNYSXGMGBS-UHFFFAOYAP
SMILES [Br-].[NH4+]
Properties
Chemical formula	NH4Br
Molar mass	97.94 g/mol
Appearance	white powder, hygroscopic
Density	2.429 g/cm3
Melting point	235 °C (455 °F; 508 K)
Boiling point	452 °C (846 °F; 725 K)
Solubility in water	60.6 g/100 mL (0 °C) 78.3 g/100 mL (25 °C) 145 g/100 mL (100 °C)
Magnetic susceptibility (χ)	−47.0×10−6 cm3/mol
Refractive index (nD)	1.712
Structure
Crystal structure	Isometric
Hazards
GHS labelling:
Pictograms	[1]
Signal word	Warning
Hazard statements	H315, H319, H335[1]
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
NFPA 704 (fire diamond)	2 0 0
Related compounds
Other anions	Ammonium fluoride Ammonium chloride Ammonium iodide
Other cations	Sodium bromide Potassium bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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)₂

Reactions

Ammonium bromide is a weak acid with a pK_a of approximately 9 in water. It is an acid salt because the ammonium ion hydrolyzes slightly in water.

Ammonium bromide is a strong electrolyte when put in water:

NH₄Br(s) → NH+4(aq) + Br⁻(aq)

Ammonium bromide decomposes to ammonia and hydrogen bromide when heated at elevated temperatures:

NH₄Br → NH₃ + HBr

Uses

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.^[2]