Xenon tetroxide
From Wikipedia, the free encyclopedia
| Xenon tetroxide | |
|---|---|
 |
 |
| IUPAC name | xenon tetraoxide xenon(VIII) oxide |
| Structure | |
| Molecular shape | Tetrahedral[1] |
| Dipole moment | 0 D |
| Properties | |
| Molecular formula | XeO4 |
| Molar mass | 195.29 g mol−1 |
| Appearance | Yellow solid below −36°C |
| Density | ? g cm−3, solid |
| Melting point |
−35.9 °C |
| Boiling point |
0 °C decomp.[citation needed] |
| Solubility in water | Soluble |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
? kJ mol−1 |
| Standard molar entropy S |
? J.K−1.mol−1 |
| Hazards | |
| EU classification | Explosive (E) |
| Related compounds | |
| Related compounds | Perxenic acid Xenon trioxide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
|
Xenon tetroxide (molecular formula XeO4) is a yellow crystalline solid that is stable below −35.9 °C.[2][3] The xenon atom has an oxidation state of +8 and oxygen of −2. All eight valence shell electrons of xenon are involved, making it an unstable compound. Above -35.9°C it explodes to give xenon and oxygen gas. Oxygen is the only element that can bring xenon up to its highest oxidation state; even fluorine can only give XeF6, probably for steric reasons. Xenon tetroxide dissolves in water[citation needed] to give perxenic acid, and in alkalis[citation needed] to give the perxenate ion.
Another known oxide is xenon trioxide. The dioxide remains elusive and only the XeOO+ cation has been identified by infrared spectroscopy in solid argon[4].
[edit] Reactions
A spontaneous explosion occurs at temperature above −35.9 °C , with ΔH = -643 kJ/mol.
- XeO4 → Xe + 2 O2
The two other short lived xenon compounds with an oxidation state of +8 are accessible by the reaction of xenon tetroxide with xenon hexafluoride. XeO3F2 and XeO2F4 can be detected with mass spectroscopy.
[edit] Synthesis
All syntheses start from the perxenates, which are accessible from the xenates through two methods. One is disproportionation of xenates to perxenates and xenon:
- 2 XeO42− → XeO64− + Xe + O2.
The other is oxidation of the xenates with ozone:
- 2 XeO42− + 4 e- + 2 O3 → 2 XeO64- + 2 O2.
Barium perxenate is reacted with sulfuric acid and the unstable perxenic acid is dehydrated to give xenon tetroxide:
- Ba2XeO6 + 2 H2SO4 → 2 BaSO4 + (H4XeO6 → 2 H2O + XeO4).
The unstable perxenic acid slowly undergoes a disproportionation reaction to the xenic acid and oxygen:
- H4XeO6 → 1/2 O2 + H2XeO4 + H2O.
[edit] References
- ^ G. Gundersen, K. Hedberg, J. L.Huston (1970). "Molecular Structure of Xenon Tetroxide, XeO4". J. Chem. Phys. 52: 812-815. doi:.
- ^ H.Selig , J. G. Malm , H. H. Claassen , C. L. Chernick , J. L. Huston (1964). "Xenon tetroxide -Preparation + Some Properties". Science 143: 1322. doi:.
- ^ J. L. Huston, M. H. Studier, E.N. Sloth (1964). "Xenon tetroxide - Mass Spectrum". Science 143: 1162. doi:.
- ^ M. Zhou, Y. Zhao, Y. Gong, J. Li (2006). "Formation and Characterization of the XeOO+ Cation in Solid Argon". J. Am. Chem. Soc. 128: 2504-2505. doi:.
- Lide, D. R. (ed.) (2002). CRC Handbook of Chemistry and Physics, 83rd ed., Boca Raton, FL: CRC Press.
