Technetium(IV) oxide
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Other names
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Identifiers | |
3D model (
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ChEBI | |
ChemSpider | |
873611 | |
PubChem CID
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Properties | |
TcO2 | |
Molar mass | 130.00 g/mol |
Appearance | Black solid |
Density | 6.9 g/cm3[1] |
Melting point | 1,100 °C (2,010 °F; 1,370 K)[3] (sublimes) |
Insoluble | |
Solubility | Slightly soluble in acid (dihydrate)[2] |
Structure | |
Isostructural to MoO2[1] | |
Thermochemistry | |
Gibbs free energy (ΔfG⦵)
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−305.974±3.377[clarification needed units] (dihydrate) |
Related compounds | |
Other anions
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Technetium(IV) chloride |
Related compounds
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Technetium(VII) oxide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Technetium(IV) oxide, also known as technetium dioxide, is a chemical compound with the formula TcO2 which forms the dihydrate, TcO2·2H2O, which is also known as technetium(IV) hydroxide. It is a radioactive black solid which slowly oxidizes in air.[1][4]
Preparation
Technetium dioxide was first produced in 1949 by electrolyzing a solution of
- 2 NH4TcO4 → 2 TcO2 + 4 H2O + N2
All of these methods except the last lead to the formation of the dihydrate. The most modern method of producing this compound is by the reaction of ammonium pertechnetate with sodium dithionite.[8]
Properties
The dihydrate dehydrates to anhydrous technetium dioxide at 300 °C, and if further heated sublime at 1,100 °C under an inert atmosphere, however, if oxygen is present, it will react with the oxygen to produce technetium(VII) oxide at 450 °C.[1][3][7] If water is present, pertechnetic acid is produced by the reaction of technetium(VII) oxide with water.[6]
If technetium dioxide is treated with a base, such as sodium hydroxide, it forms the hydroxotechnetate(IV) ion, which is easily oxidized to pertechnetic acid in numerous ways, such as the reaction with alkaline hydrogen peroxide, concentrated nitric acid, bromine, or tetravalent cerium.[1][7]
The solubility of technetium(IV) oxide is very low and is reported to be 3.9 μg/L. The main species when technetium dioxide is dissolved in water is TcO2+ at pH below 1.5, TcO(OH)+ pH between 1.5 and 2.5, TcO(OH)2 pH between 2.5 and 10.9, and TcO(OH)–
3 above pH 10.9. The solubility can be affected by adding various organic ligands such as
If technetium dioxide is electrolyzed in acidic conditions, the following reaction occurs:
- TcO2·2H2O → TcO–
4 + 4 H+ + 3 e–
The electrode potential measured for this reaction is −837.2±10.0 kJ/mol.[2]
The molar magnetic susceptibility of TcO2·2H2O was found to be χm = 244×106[clarification needed units].[3]
References
- ^ ISBN 9780080578606.
- ^ S2CID 98137163. Retrieved 4 November 2022.
- ^ .
- ^ OSTI 4073069. Retrieved 4 November 2022.
- .
- ^ .
- ^ .
- S2CID 96789279.
- PMID 21539349.