Telluric acid


Telluric acid
Telluric acid
Identifiers
CAS number 7803-68-1
PubChem 61609
ChemSpider 55517 YesY
ChEBI CHEBI:30463 YesY
Jmol-3D images Image 1
Properties
Molecular formula H6O6Te
Molar mass 229.64 g/mol
Appearance White monoclinic crystals
Density 3.07 g/cm3
Melting point

136°C (409.15 K)

Solubility in water 50.1 g/100 ml at 30°C[1]
Acidity (pKa) 7.68, 11.0 at 18°C[2]
Structure
Molecular shape octahedral
Dipole moment 0 D
Hazards
Main hazards corrosive
Related compounds
Other anions hydrotelluric acid
tellurous acid
hydrogen telluride
Related compounds Teflic acid,
Sulfuric acid
Selenic acid
 YesY acid (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Telluric acid is a chemical compound with the formula Te(OH)6. It is a white solid made up of octahedral Te(OH)6 molecules which persist in aqueous solution.[3] There are two forms, rhombohedral and monoclinic, and both contain octahedral Te(OH)6 molecules.[4] Telluric acid is a weak acid which is dibasic, forming tellurate salts with strong bases and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water.[4][5]

Contents

Preparation

Telluric acid is formed by the oxidation of tellurium or tellurium dioxide with a powerful oxidising agent such as hydrogen peroxide, chromium trioxide or sodium peroxide.[4]

TeO2 + H2O2 + 2H2O → Te(OH)6

Crystallisation of telluric acid solutions below 10°C gives Te(OH)6.4H2O.[3] It is oxidizing, as shown by the electrode potential for the reaction below, although it is kinetically slow in its oxidations.[4]

H6TeO6 + 2H+ + 2e TeO2 + 4H2O Eo = +1.02 V

Chlorine, by comparison, is +1.36V and selenious acid is +0.74V in oxidizing conditions.

Properties and reactions

The anhydrous acid is stable in air at 100°C but above this it dehydrates to form polymetatelluric acid, a white hygroscopic powder (approximate composition (H2TeO4)10), and allotelluric acid, an acid syrup of unknown structure (approximate composition (H2TeO4)3(H2O)4).[3]
Strong heating at over 300°C produces the α- crystalline modification of tellurium trioxide, α-TeO3. [6]
Reaction with diazomethane gives the hexamethyl ester, Te(OMe)6.[3]

Telluric acid and its salts mostly contain hexacoordinate tellurium.[4] This is true even for salts such as magnesium tellurate, MgTeO4, which is isostructural with magnesium molybdate and contains TeO6 octahedra.[4]

Other forms of telluric acid

Metatelluric acid, H2TeO4, the tellurium analogue of sulfuric acid, H2SO4, is unknown. Allotelluric acid of approximate composition H2TeO4)3(H2O)4, is not well characterised and may be a mixture of Te(OH)6 and (H2TeO4)n.[3]

Other tellurium acids

Tellurous acid, containing tellurium in its +4 oxidation state, (H2TeO3) is known but not well characterised. Hydrogen telluride is an unstable gas that forms hydrotelluric acid upon addition to water.

References

  1. ^ Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, FL: CRC Press, pp. 4–88, ISBN 0-8493-0594-2 
  2. ^ Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, FL: CRC Press, pp. 8–45, ISBN 0-8493-0594-2 
  3. ^ a b c d e Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419. 
  4. ^ a b c d e f Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5 
  5. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  6. ^ Inorganic Chemistry,Egon Wiberg, Arnold Frederick Holleman Elsevier 2001 ISBN 0-12-352651-5

Sources

  • Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5 
  • Lide, D. R., ed (2002). CRC Handbook of Chemistry and Physics (83rd ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0483-0. 

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Look at other dictionaries:

  • telluric acid — n. a heavy, white, crystalline acid, H2TeO4 …   English World dictionary

  • telluric acid — noun : an acid containing hexavalent tellurium: as a. : a very weak acid H6TeO6 that is a good oxidizing agent and is obtainable in two crystalline forms and as a tetrahydrate by oxidizing tellurium or tellurium dioxide called also orthotelluric… …   Useful english dictionary

  • telluric acid — noun Chemistry a crystalline acid made by oxidizing tellurium dioxide …   English new terms dictionary

  • telluric acid — /tɛlˌjurɪk ˈæsəd/ (say tel.yoohrik asuhd) noun a very weak dibasic acid, H6TeO6, which is a moderately strong oxidising agent …   Australian English dictionary

  • telluric acid — Chem. a white, toxic, crystalline compound, H6TeO6, slightly soluble in cold water, soluble in hot water and alkalis: used as an analytical agent. [1835 45] * * * …   Universalium

  • telluric acid — noun the hydrated form of tellurium oxide, HTeO, with some use as a reagent …   Wiktionary

  • Telluric — Tel*lu ric, a. [L. tellus, uris, the earth: cf. F. tellurique.] 1. Of or pertaining to the earth; proceeding from the earth. [1913 Webster] Amid these hot, telluric flames. Carlyle. [1913 Webster] 2. (Chem.) Of or pertaining to tellurium; derived …   The Collaborative International Dictionary of English

  • Telluric bismuth — Telluric Tel*lu ric, a. [L. tellus, uris, the earth: cf. F. tellurique.] 1. Of or pertaining to the earth; proceeding from the earth. [1913 Webster] Amid these hot, telluric flames. Carlyle. [1913 Webster] 2. (Chem.) Of or pertaining to… …   The Collaborative International Dictionary of English

  • Telluric silver — Telluric Tel*lu ric, a. [L. tellus, uris, the earth: cf. F. tellurique.] 1. Of or pertaining to the earth; proceeding from the earth. [1913 Webster] Amid these hot, telluric flames. Carlyle. [1913 Webster] 2. (Chem.) Of or pertaining to… …   The Collaborative International Dictionary of English

  • orthotelluric acid — “+... noun Etymology: orth + telluric acid : telluric acid a …   Useful english dictionary