- Telluric acid
-
Telluric acid 
Telluric(VI) acidOther namesorthotelluric acidIdentifiers CAS number 7803-68-1 PubChem 61609 ChemSpider 55517 
ChEBI CHEBI:30463 Jmol-3D images Image 1 - O[Te](O)(O)(O)(O)O
- InChI=1S/H2O4Te/c1-5(2,3)4/h(H2,1,2,3,4)
Key: XHGGEBRKUWZHEK-UHFFFAOYSA-N
InChI=1/H2O4Te/c1-5(2,3)4/h(H2,1,2,3,4)
Key: XHGGEBRKUWZHEK-UHFFFAOYAT
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 tellurideRelated compounds Teflic acid,
Sulfuric acid
Selenic acid
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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 E
o= +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
- ^ Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, FL: CRC Press, pp. 4–88, ISBN 0-8493-0594-2
- ^ Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, FL: CRC Press, pp. 8–45, ISBN 0-8493-0594-2
- ^ a b c d e Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419.
- ^ 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
- ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ 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.
Hydrogen compounds H3AsO3 · H3AsO4 · HAt · HSO3F · HBF4 · HBr · HBrO · HBrO2 · HBrO3 · HBrO4 · HCl · HClO · HClO2 · HClO3 · HClO4 · HCN · HCNO · H2CrO4/H2Cr2O7 · H2CO3 · H2CS3 · HF · HFO · HI · HIO · HNC · HNCO · HNO · HNO3 · H2N2O2 · HNO5S · H3NSO3 · H2O · H2O2 · H2O3 · H3PO2 · H3PO3 · H3PO4 · H4P2O7 · H5P3O10 · H2PtCl6 · H2S · H2Se · H2SeO3 · H2SeO4 · H4SiO4 · H2SiF6 · H2SO3 · H2SO4 · H2SO5 · H2S2O3 · H2S2O6 · H2S2O7 · H2S2O8 · CF3SO3H · H2Te · H2TeO3 · H6TeO6 · H4TiO4 · H2Po · H3VO4 · HCo(CO)4
Categories:- Hydrogen compounds
- Tellurates
- Oxidizing acids
- Oxidizing agents
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