Hydrobromic acid
| General | ||||||||||
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| Surname | Hydrobromic acid | |||||||||
| other names |
Hydrobromic acid |
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| Molecular formula | HBr (aq) | |||||||||
| Brief description |
colorless liquid that smokes in high concentrations |
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| External identifiers / databases | ||||||||||
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| properties | ||||||||||
| Molar mass | 80.91 g mol −1 | |||||||||
| Physical state |
liquid |
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| density |
1.48 g cm −3 (47.63%) |
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| boiling point |
126 ° C (47.63%, azeotrope) |
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| pK s value |
−9 |
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| safety instructions | ||||||||||
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||
Hydrobromic acid refers to the solutions of gaseous hydrogen bromide (HBr) in water. Like the other hydrohalic acids, the solutions react strongly acidic.
In chemical symbol language, HBr is understood to mean both the gas and its aqueous solution . Where a distinction or a more precise identification of the aqueous solution is required, the abbreviation aq is used to find designations such as B. HBr (aq) , HBr aq, HBr aq or HBr aq .
properties
Hydrobromic acid behaves very similarly to the chemically related hydrochloric acid . Like the gaseous hydrogen chloride HCl, the colorless gas HBr easily dissolves in water, whose solubility at standard pressure for HBr decreases with increasing water temperature until it corresponds to the composition of the azeotrope described below.
| Temperature of the water in ° C |
Solubility of HBr in water (liter HBr / liter H 2 O) |
|---|---|
| 0 | 612 |
| 10 | 582 |
| 25th | 533 |
| 50 | 468 |
| 75 | 406 |
| 100 | 345 |
An aqueous solution with a maximum of 65 percent HBr (mass fraction) and a density of 1.7675 g / cm 3 is thus obtained at room temperature . Solutions with 40–65% are customary. HBr and water (like HCl) form a positive azeotrope at 47.63% HBr and 52.37% H 2 O, which boils at 126 ° C; the density of this solution is 1.482 g / cm 3 . This ratio at the azeotropic point can no longer be changed by simple distillation, since the liquid and gas phases have the same composition. The 48%, constant-boiling acid is 8.89 molar.
Density of hydrobromic acid solutions at 20 ° C concentration in mass% 10 20th 30th 40 50 60 65 density in g cm −3 1.0723 1.1579 1.2580 1.3772 1.5173 1.6787 1.7675
Since hydrobromic acid is a very strong acid, the HBr molecule is almost completely dissociated in aqueous solution, it is split into the cation H + and the anion Br - :
Since H + ions are not isolated in aqueous solution, but instead combine with water molecules, these are often roughly written as H 3 O + . If this is taken into account, the following equation is obtained for the solution of HBr in water.
The H 3 O + ion is also known as the oxonium ion (earlier names: hydroxonium ion or hydronium ion).
Like hydrochloric acid, hydrobromic acid dissolves most metals and metal oxides to form bromides . Hydrobromic acid and its vapors are highly corrosive. Even stainless steel forms “flash rust” within 24 hours if it is in contact with HBr vapors. In contrast to hydrochloric acid, hydrobromic acid is of little economic importance and is hardly used in the chemical industry.
Web links
Individual evidence
- ↑ Entry on hydrobromic acid. In: Römpp Online . Georg Thieme Verlag, accessed on December 25, 2014.
- ^ A b A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .
- ↑ chem.wisc.edu: pKa Data , Compiled by R. Williams (PDF, 78 kB).
- ↑ a b Entry on hydrobromic acid in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
- ↑ Entry on hydrobromic acid…% in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
- ↑ Yoffe, D .; Frim, R .; Ukeles, SD; Dagani, MJ; Barda, HJ; Benya, TJ; Sanders, DC: Bromine Compounds , in: Ullmanns Enzyklopädie der Technischen Chemie , Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2013; doi : 10.1002 / 14356007.a04_405.pub2 .