Ammonium bromide

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Ammonium bromide
Ammonium bromide.png
ball-and-stick model of an ammonium cation (left) and a bromide anion (right)
Identifiers
CAS number 12124-97-9 YesY
ChemSpider 23804 YesY
UNII R0JB3224WS YesY
RTECS number BO9155000
Jmol-3D images Image 1
Properties
Molecular formula NH4Br
Molar mass 97.94 g/mol
Appearance white powder, hygroscopic
Density 2.429 g/cm3
Melting point 452 °C (846 °F; 725 K)
Boiling point 235 °C (455 °F; 508 K)
Solubility in water 60.6 g/100 mL (0 °C)
78.3 g/100 mL (25 °C)
145 g/100 mL (100 °C)
Refractive index (nD) 1.712
Structure
Crystal structure Isometric
Hazards
GHS pictograms GHS-pictogram-exclam.svg[1]
GHS hazard statements H319[1]
GHS precautionary statements P305+351+338
EU Index Not listed
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Other anions Ammonium fluoride
Ammonium chloride
Ammonium iodide
Other cations Sodium bromide
Potassium bromide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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).

Preparation[edit]

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[edit]

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 + HBr

Uses[edit]

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]

References[edit]

  1. ^ a b Sigma-Aldrich Co., Ammonium bromide. Retrieved on 2013-07-20.
  2. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8