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Hydrobromic acid
Hydrobromic acid
CAS number 10035-10-6 Yes check.svgY
EC number 233-113-0
RTECS number MW3850000
Molecular formula HBr
Molar mass 80.91 g/mol
Appearance colorless liquid
Density variable
Melting point


Boiling point


Solubility in water aqueous solution
Acidity (pKa) −9
EU Index 035-002-01-8
EU classification Corrosive (C)
R-phrases R34, R37
S-phrases (S1/2), S7/9, S26, S45
NFPA 704
NFPA 704.svg
Flash point Non-flammable
Related compounds
Other anions Hydrofluoric acid
Hydrochloric acid
Hydroiodic acid
Related compounds Hydrogen bromide
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Hydrobromic acid is a strong acid formed by dissolving the diatomic molecule hydrogen bromide in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at 124.3 °C and contains 47.6% HBr by weight. Hydrobromic acid has a pKa of −9, making it a stronger acid than hydrochloric acid, but not as strong as hydroiodic acid. Hydrobromic acid is one of the strongest mineral acids known.



Hydrobromic acid is mainly used for the production of inorganic bromides, especially the bromides of zinc, calcium, and sodium. It is a useful reagent for generating organobromine compounds. Certain ethers are cleaved with HBr. It also catalyzes alkylation reactions and the extraction of certain ores. Industrially significant organic compounds prepared from hydrobromic acid include allyl bromide, tetrabromobis(phenol), and bromoacetic acid.[1] doi:10.1002/14356007.a04_405.


Hydrobromic acid can be prepared in the laboratory via the reaction of Br2, SO2, and water.[2] More typically laboratory preparations involve the production of anhydrous HBr, which is then dissolved in water.

Hydrobromic acid has commonly been prepared industrially by reacting bromine with either sulfur or phosphorus and water. However, it can also be produced electrolytically.[2]. It can also be prepared by treating bromides with non-oxidising acids like phosphoric or acetic acids.

Hydrobromic acid is available commercially in various concentrations and purities.


  1. ^ Michael J. Dagani, Henry J. Barda, Theodore J. Benya, David C. Sanders "Bromine Compounds" in Ullmann's Encyclopedia of Industrial Chemistry" Wiley-VCH, Weinheim, 2000.
  2. ^ a b Scott, A. (1900). "Preparation of pure hydrobromic acid". J. Chem. Soc., Trans. 77: 648–650. doi:10.1039/ct9007700648.  

External links

As a three letter acronym, HBR can be:

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