- Hydrogen bromide
Colorless, smoking in moist air gas with a pungent odor
3.6452 kg · m 3 (0 ° C, 1013 hPa)
-86.9 ° C
-66.4 ° C
2.00 MPa ( 20 ° C)
Good in water ( 700 g · l-1 at 20 ° C)
0.8272 (3 ) D ( 2.76 · 10-30 C · m)
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Hydrogen bromide is a colorless gas, which forms in moist air fog, because the combination of bromine and hydrogen dissolves well in water, forming hydrobromic acid.
Hydrogen bromide may be represented by means of a substitution reaction. One example is the reaction of toluene with bromine. By heating or by light bromine reacts with the toluene, inter alia, to benzyl bromide and hydrogen bromide, whereby the liquid was brown, in advance, is decolorized.
Also from sodium bromide can be released. For this purpose, concentrated phosphoric acid is added dropwise at a slightly elevated temperature on the solid.
Alternatively, acetic acid can be used instead of phosphoric acid:
Reaction with water
If hydrogen bromide dissolved in water, dissociates the hydrogen bromide molecule are formed oxonium ion and bromide ion. Therefore, the pH - value decreases, the solution reacts as a strong acid.
Acid formation of hydrogen bromide gas in water is irritating and toxic to eyes and respiratory tract and in high concentration. However, (gas) poisoning is rare because it (see above) is usually used as an aqueous solution and rapidly forming fog after eventual outgassing. Complete combustion of brominated organic substances, besides hydrogen bromide and elemental bromine arise, which is much more toxic.