Uranium hexafluoride

Uranium hexafluoride
Names



IUPAC names Uranium hexafluoride Uranium(VI) fluoride
Identifiers
CAS Number	7783-81-5^Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:30235^Y
ChemSpider	22966^Y
ECHA InfoCard	100.029.116
PubChem	24560
RTECS number	YR4720000
UN number	2978 (<1% ²³⁵U) 2977 (>1% ²³⁵U)
InChI InChI=1S/6FH.U/h61H;/q;;;;;;+6/p-6^Y Key: SANRKQGLYCLAFE-UHFFFAOYSA-H^Y InChI=1/6FH.U/h61H;/q;;;;;;+6/p-6/rF6U/c1-7(2,3,4,5)6 Key: SANRKQGLYCLAFE-IIYYNVFAAT
SMILES F[U](F)(F)(F)(F)F
Properties
Chemical formula	UF₆
Molar mass	352.02 g/mol
Appearance	colorless solid
Density	5.09 g/cm³, solid
Melting point	64.052 °C (147.294 °F; 337.202 K) (triple point at 151 kPa)
Boiling point	56.5 °C (133.7 °F; 329.6 K) (sublimes)
Solubility in water	Reacts violently
Solubility	soluble in chloroform, CCl₄, liquid chlorine and bromine dissolves in nitrobenzene
Structure
Crystal structure	Orthorhombic, oP28
Space group	Pnma, No. 62
Coordination geometry	octahedral (O_h)
Dipole moment	0
Thermochemistry
Std molar entropy (S^o₂₉₈)	– solid: −430,4 ± 1,5 J·K⁻¹·mol⁻¹ – gaseous: −280,4 ± 1,5 J·K⁻¹·mol⁻¹
Std enthalpy of formation (Δ_fH^o₂₉₈)	– solid: −(2197,7 ± 1,8) kJ·mol⁻¹ – gaseous: −(2148,1 ± 1,8) kJ·mol⁻¹
Hazards
Safety data sheet	ICSC 1250
EU classification (DSD)	T+ (T+) N (N)
R-phrases	R26/28, R33, R51/53
S-phrases	(S1/2), S20/21, S45, S61
Flash point	Non-flammable
Related compounds
Other anions	Uranium hexachloride
Other cations	Neptunium hexafluoride Plutonium hexafluoride
Related uranium fluorides	Uranium(III) fluoride Uranium(IV) fluoride Uranium(V) fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y (what is ^YN ?)
Infobox references

– gaseous: −280,4 ± 1,5 J·K⁻¹·mol⁻¹

– gaseous: −(2148,1 ± 1,8) kJ·mol⁻¹

Uranium hexafluoride (U F₆), referred to as "hex" in the nuclear industry, is a compound used in the uranium enrichment process that produces fuel for nuclear reactors and nuclear weapons. It forms solid grey crystals at standard temperature and pressure, is highly toxic, reacts violently with water and is corrosive to most metals. It reacts mildly with aluminium, forming a thin surface layer of AlF₃ that resists further reaction.

Milled uranium ore—U₃O₈ or "yellowcake"—is dissolved in nitric acid, yielding a solution of uranyl nitrate UO₂(NO₃)₂. Pure uranyl nitrate is obtained by solvent extraction, then treated with ammonia to produce ammonium diuranate ("ADU", (NH₄)₂U₂O₇). Reduction with hydrogen gives UO₂, which is converted with hydrofluoric acid (HF) to uranium tetrafluoride, UF₄. Oxidation with fluorine yields UF₆.

During nuclear reprocessing, uranium is reacted with chlorine trifluoride to give UF₆:

At atmospheric pressure, it sublimes at 56.5 °C.

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