Tellurous acid
| Tellurous Acid | |
| Names | |
|---|---|
| IUPAC name
Tellurous acid
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| Other names
Tellurium dioxide hydrate, tellurium(IV) oxide hydrate
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| Identifiers | |
10049-23-7  |
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| ChEBI | CHEBI:30465  |
| ChemSpider | 23310 |
| Jmol 3D model | Interactive image |
| PubChem | 24936 |
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| Properties | |
| H2TeO3 | |
| Molar mass | 177.616 grams |
| Appearance | colorless crystals |
| Density | ~ 3 g/cm3 |
| Boiling point | decomposes |
| negligible | |
| Acidity (pKa) | pKa(1) = 2.48, pKa(2) = 7.70 [1] |
| Structure | |
| unknown | |
| pyramidal at Te | |
| Vapor pressure | {{{value}}} |
| Related compounds | |
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Other anions
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Selenous acid Sulfurous acid |
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Other cations
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Sodium tellurite |
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Related compounds
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Telluric acid Selenic acid Sulfuric acid |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 verify (what is ?) |
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| Infobox references | |
Tellurous acid is an inorganic compound with the formula H2TeO3. It is the oxoacid of tellurium(IV).[2] The compound is not well characterized. An alternative way of writing its formula is (HO)2TeO. In principle, tellurous acid would form by treatment of tellurium dioxide with water, i.e. hydrolysis. The related conjugate base is well known in the form of several salts such as potassium acid tellurite, KHTeO3.
Preparation
Tellurium dissolves violently in pure nitric acid of density 1.25. "If after the first five minutes, the clear liquid be poured into water, tellurous acid is precipitated in white flocks. But if not immediately precipitated the nitric acid solution undergoes a change."
Properties
In contrast to the analogous compound Selenous acid, Tellurous acid is only metastable. Most tellurite salts contain the TeO32− ion. Oxidation of its aqueous solution with hydrogen peroxide gives the tellurate ion. It is usually prepared as an aqueous solution where it acts as a weak acid. [1]
- H2TeO3 + H2O ⇄ H3O+ + HTeO3- Ka1 = 2 x 10-3
- HTeO3- + H2O ⇄ H3O+ + TeO32- Ka2 = 1 x 10-8[4]
References
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