Iodic acid
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| General | ||||||||||||||||
| Surname | Iodic acid | |||||||||||||||
| other names |
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| Molecular formula | HIO 3 | |||||||||||||||
| Brief description |
colorless, rhombic, piezoelectric crystals |
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| properties | ||||||||||||||||
| Molar mass | 175.91 g mol −1 | |||||||||||||||
| Physical state |
firmly |
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| density |
4.63 g cm −3 |
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| Melting point |
110 ° C (decomposition) |
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| pK s value |
0.804 |
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| solubility |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||||||||
Iodic acid , and iodic acid , is a halogen oxygen acid such as perchloric acid and bromic . It is the only one of the halogen (V) acids of the HXO 3 type that can be isolated anhydrous.
Manufacturing
Iodic acid is obtained by oxidizing iodine with strong oxidizing agents such as nitric acid (HNO 3 ), chlorine , chloric acid or hydrogen peroxide (H 2 O 2 ):
The hydrochloric acid formed must be removed from the equilibrium , as it would reduce the iodic acid due to the reverse reaction and shift the equilibrium to the left. This can be achieved, for example, with mercury (II) oxide (HgO).
properties
According to the VSEPR model , iodic acid has a trigonal pyramidal structure. Iodic acid forms transparent, colorless, rhombic crystals that dissolve very easily in water. The substance is a medium strong acid with a pKa value of 0.804 and has a strong oxidizing effect. Iodic acid is polymorphic . In addition to the thermodynamically stable, non- centrosymmetrical α-form, there is also a metastable , centrosymmetrical γ-form.
Iodates
Iodates are the salts of iodic acid of the general formula M (IO 3 ) n (M = metal, n = depending on the valency of the metal). They are more stable than chlorates and bromates , but like these, strong oxidizing agents. Iodic acid can beliberatedfrom iodate by reaction with sulfuric acid .
safety instructions
Iodic acid and iodates are very strong oxidizing agents and can react explosively with reducing substances such as sulfur, metal powder or organic substances.
Individual evidence
- ↑ a b entry on iodic acid. In: Römpp Online . Georg Thieme Verlag, accessed on July 14, 2014.
- ↑ Iodic acid data sheet from Sigma-Aldrich , accessed on May 13, 2017 ( PDF ).
- ↑ a b c d Entry on iodic acid in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .
- ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .
- ↑ G. Brauer (ed.), Handbook of Preparative Inorganic Chemistry 2nd ed., Volume 1, Academic Press 1963, pp. 316-8.
- ↑ A. Fischer, M. Lindsjö: γ-HIO 3 - a metastable, centrosymmetric polymorph of iodic acid. In: Journal of Inorganic and General Chemistry . 631 (9), 2005, pp. 1574-1576, doi: 10.1002 / zaac.200500099 .