Tellurous acid

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, that is by hydrolysis. The related conjugate base is well known in the form of several salts such as potassium hydrogen tellurite, KHTeO3.

Tellurous acid
Names
IUPAC name
Tellurous acid
Other names
Tellurium dioxide hydrate, tellurium(IV) oxide hydrate
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.030.145
UNII
Properties
H2TeO3
Molar mass 177.616 grams
Appearance colorless crystals
Density ~ 3 g/cm3
Boiling point decomposes
negligible
Acidity (pKa) pKa1 = 2.48, pKa2 = 7.70 [1]
Conjugate base Tellurite
Structure
unknown
pyramidal at Te
Related compounds
Other anions
 Selenous acid
Sulfurous acid
Other cations
 Sodium tellurite
Related compounds
 Telluric acid
Selenic acid
Sulfuric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Properties

In contrast to the analogous compound selenous acid, tellurous acid is only metastable. Most tellurite salts contain the TeO2−
3 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][3]

H2TeO3 + H2O ⇌ H3O+ + HTeO−
3 Ka1 = 2×10−3
HTeO−
3 + H2O ⇌ H3O+ + TeO2−
3 Ka2 = 1×10−8
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References
  1. Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 16: The group 16 elements". Inorganic Chemistry (3rd ed.). Pearson. p. 524. ISBN 978-0-13-175553-6.
  2. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  3. http://www.austincc.edu/chemlab/weakacid
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