Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and Telluric acid: Difference between pages

{{Short description|Chemical compound (Te(OH)6)}}

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| verifiedrevid = 470481521

| = Telluric acid

| ImageSize = 150px

| ImageName = [[Skeletal formula]] of ortho-telluric acid

| ImageFile1 = Telluric-acid-3D-balls.png

| ImageSize1 = 150px

| ImageName1 = [[Ball-and-stick model]] of ortho-telluric acid

| IUPACName = Hexahydroxidotellurium

| OtherNames = {{ubl|Orthotelluric acid|Hexahydroxytellurium|Hexahydroxy-λ⁶-tellane|Tellurium hexahydroxide|Tellurium(VI) hydroxide}}

|Section1={{Chembox Identifiers

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| CASNo_Ref = {{cascite|correct|}}

| CASNo = 7803-68-1

| UNII_Ref = {{fdacite|correct|FDA}}

| =

| PubChem = 62686

| RTECS =

|Section2={{Chembox Properties

| Formula = 6

| Te=1|O=6|H=6

| Appearance = White [[monoclinic]] crystals

| Density = 3.07 g/cm³

| = 136

| MeltingPt_notes =

| pKa = 7.5, 11, 14<ref name=P82db>{{cite book|title=Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution|editor-first=D.&nbsp;D.|editor-last=Perrin|edition=2nd|series=[[IUPAC]] Chemical Data|issue=29|publisher=Pergamon|location=Oxford|year=1982|publication-date=1984|orig-date=1969|lccn=82-16524|isbn=0-08-029214-3|at=Entry&nbsp;219}}</ref>

| Solubility = 50.1 g/(100 ml) at 30 °C<ref name=CRC>

| last = Lide

| first = David R.

| author-link =

| =

| title = Handbook of Chemistry and Physics

| edition = 87

| volume =

| =

| publication-place = Boca Raton, Florida

| publisher = CRC Press

| =

| isbn = 0-8493-0594-2

| =

| oclc =

| =

| url =

| =

| ConjugateBase = [[Tellurate]]

|Section3={{Chembox Structure

| MolShape = octahedral

| CrystalStruct =

| Dipole = 0 [[Debye|D]]

|Section7={{Chembox Hazards

| =

| MainHazards = corrosive

| =

| =

| GHS_ref =

}}

|Section8={{Chembox Related

| OtherCations =

| = [[ acid]]<br>[[ acid]]<br>[[ ]]

| OtherCompounds = [[Teflic acid]]<br />[[Sulfuric acid]]<br />[[Selenic acid]]

'''Telluric acid''', or more accurately '''[[Ortho acid|ortho]]telluric acid''', is a [[chemical compound]] with the [[chemical formula|formula]] {{chem2|Te(OH)6}}, often written as {{chem2|H6TeO6}}. It is a white crystalline solid made up of octahedral {{chem2|Te(OH)6}} molecules which persist in aqueous solution.<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref> In the solid state, there are two forms, rhombohedral and monoclinic, and both contain octahedral {{chem2|Te(OH)6}} molecules,<ref name = "Cotton">{{Cotton&Wilkinson6th}}</ref> containing one hexavalent [[tellurium]] (Te) atom in the +6 oxidation state, attached to six [[hydroxyl]] (–OH) groups, thus, it can be called tellurium(VI) hydroxide.

Telluric acid is a [[weak acid]] which is [[polyprotic acid|dibasic]], forming [[tellurate]] [[salt (chemistry)|salt]]s with [[strong base]]s and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water.<ref name = "Cotton"/><ref name=holleman>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}.</ref> It is used as tellurium-source in the synthesis of oxidation catalysts.

==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]].<ref name = "Cotton"/>

:{{chem2|TeO2 + H2O2 + 2 H2O → Te(OH)6}}

Crystallization of telluric acid solutions below 10&nbsp;°C gives telluric acid tetrahydrate {{chem2|Te(OH)6*4H2O}}.<ref name = "Greenwood"/>

It is an oxidising agent, as shown by the [[electrode potential]] for the reaction below, although it is kinetically slow in its oxidations.<ref name = "Cotton"/>

:{{chem2|Te(OH)6 + 2 H+ + 2 e- ⇌ TeO2 + 4 H2O}}, ''E''^<s>o</s> = +1.02&nbsp;V

[[Chlorine]], by comparison, is +1.36&nbsp;V and [[selenous acid]] is +0.74&nbsp;V in oxidizing conditions.

==Properties and reactions==

The anhydrous acid is stable in air at 100&nbsp;°C but above this it dehydrates to form polymetatelluric acid, a white hygroscopic powder (approximate composition {{chem2|(H2TeO4)10}}), and allotelluric acid, an acid syrup of unknown structure (approximate composition {{chem2|3*H2TeO4*4H2O}}).<ref>{{cite journal|doi=10.1107/S0567740879011286|title=Structure of an adduct of orthotelluric acid and urea|journal=Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry|volume=35|issue=12|pages=3039–3041|year=1979|last1=Loub|first1=J.|last2=Haase|first2=W.|last3=Mergehenn|first3=R.|bibcode=1979AcCrB..35.3039L }}</ref><ref name = "Greenwood"/>

Typical salts of the acid contains the anions {{chem2|[Te(O)(OH)5]−}} and {{chem2|[Te(O)2(OH)4](2−)}}. The presence of the tellurate ion {{chem2|TeO4(2−)}} has been confirmed in the solid state structure of {{chem2|Rb6[TeO5][TeO4]}}.<ref name="InorgChem">{{cite book

| title = Inorganic Chemistry, 3rd Edition

| chapter = Chapter 16: The group 16 elements

| author1 = Catherine E. Housecroft

| author2 = Alan G. Sharpe

| publisher = Pearson

| year = 2008

| isbn = 978-0-13-175553-6

| page = 526

}}</ref>

Strong heating at over 300&nbsp;°C produces the α crystalline modification of [[tellurium trioxide]], α-{{chem2|TeO3}}.

<ref name = holleman/> Reaction with [[diazomethane]] gives the hexamethyl ester, {{chem2|Te(OCH3)6}}.<ref name = "Greenwood"/>

Telluric acid and its salts mostly contain hexacoordinate [[tellurium]].<ref name = "Cotton"/> This is true even for salts such as magnesium tellurate, {{chem2|MgTeO4}}, which is isostructural with magnesium molybdate and contains {{chem2|TeO6}} octahedra.<ref name = "Cotton"/>

==Other forms of telluric acid==

Metatelluric acid, {{chem2|H2TeO4}}, the tellurium analogue of [[sulfuric acid]], {{chem2|H2SO4}}, is unknown. Allotelluric acid of approximate composition {{chem2|3*H2TeO4*4H2O}}, is not well characterised and may be a mixture of {{chem2|Te(OH)6}} and {{chem2|(H2TeO4)_{''n''}|}}.<ref name = "Greenwood"/>

==Other tellurium acids==

[[Tellurous acid]] {{chem2|H2TeO3}}, containing tellurium in its +4 oxidation state, is known but not well characterised.

[[Hydrogen telluride]] is an unstable gas that forms [[hydrotelluric acid]] upon addition to water.

==References==

{{reflist}}

{{Hydrogen compounds}}

{{Hydroxides}}

{{Authority control}}

[[Category:Hydroxides]]

[[Category:Tellurates]]

[[Category:Oxidizing acids]]

[[Category:Chalcogen oxoacids]]