Rubidium fluoride
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| Other names Rubidium(I) Fluoride | |
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| ECHA InfoCard | 100.033.262  |
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| Properties | |
Chemical formula | RbF |
| Molar mass | 104.4662 g/mol |
| Appearance | white crystalline solid |
| Density | 3.557 g/cm3 |
| Melting point | 795 °C (1,463 °F; 1,068 K) |
| Boiling point | 1,408 °C (2,566 °F; 1,681 K) |
Solubility in water | 130.6 g/100 mL (18 °C) |
Magnetic susceptibility (χ) | −31.9·10−6 cm3/mol |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Toxic |
| NFPA 704 (fire diamond) |  3 0 0 |
| Flash point | Non-flammable |
| Related compounds | |
Other anions | Rubidium chloride Rubidium bromide Rubidium iodide Rubidium astatide |
Other cations | Lithium fluoride Sodium fluoride Potassium fluoride Caesium fluoride Francium fluoride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).  Y verify (what is  Y N ?) Infobox references | |
Chemical compound
Rubidium fluoride (RbF) is the fluoride salt of rubidium. It is a cubic crystal with rock-salt structure.
Synthesis
There are several methods for synthesising rubidium fluoride. One involves reacting rubidium hydroxide with hydrofluoric acid:[1]
- RbOH + HF → RbF + H2O
Another method is to neutralize rubidium carbonate with hydrofluoric acid:[1]
- Rb2CO3 + 2HF → 2RbF + H2O + CO2
Another possible method is to react rubidium hydroxide with ammonium fluoride:
- RbOH + NH4F → RbF + H2O + NH3
The least used method due to expense of rubidium metal is to react it directly with fluorine gas, as rubidium reacts violently with halogens:[1]
- 2Rb + F2 → 2RbF
Properties
Rubidium fluoride is a white crystalline substance with a cubic crystal structure that looks very similar to common salt (NaCl). The crystals belong to the space group Fm3m (space group no. 225) with the lattice parameter a = 565 pm and four formula units per unit cell.[2] The refractive index of the crystals is nD = 1.398.[2] Rubidium fluoride colors a flame (Bunsen burner flame) purple or magenta red (spectral analysis).
Rubidium fluoride forms two different hydrates, a sesquihydrate with the stoichiometric composition 2RbF·3H2O and a third hydrate with the composition 3RbF·H2O.[3]
In addition to simple rubidium fluoride, an acidic rubidium fluoride with the molecular formula HRbF2 is also known,[4] which can be produced by reacting rubidium fluoride and hydrogen fluoride.[4] The compounds H2RbF3 and H3RbF4 were also synthesized.[5][4]
The solubility in acetone is 0.0036 g/kg at 18 °C and 0.0039 g/kg at 37 °C.[6]
The standard enthalpy of formation of rubidium fluoride is ΔfH0298 = −552.2 kJ mol−1,[7] the standard free enthalpy of formation ΔG0298 = −520.4 kJ mol−1,[7] and the standard molar entropy S0298 = 113.9 J K −1 ·mol−1.[7] The enthalpy of solution of rubidium fluoride was determined to be −24.28 kJ/mol.[8]
References
- ^ a b c "WebElements". Archived from the original on 2008-04-18. Retrieved 23 February 2006.
- ^ a b Ans, Jean d'; Lax, Ellen (1998). Taschenbuch für Chemiker und Physiker (in German). Springer. ISBN 978-3-540-60035-0.
- ^ texte, Académie des sciences (France) Auteur du (1911-01-01). "Comptes rendus hebdomadaires des séances de l'Académie des sciences / publiés... par MM. les secrétaires perpétuels". Gallica. Retrieved 2023-12-24.
- ^ a b c Eggeling, Hans; Meyer, Jullius (1905-08-19). "Über die Fluoride des Rubidiums". Zeitschrift für anorganische Chemie. 46 (1): 174–176. doi:10.1002/zaac.19050460111. ISSN 0863-1778.
- ^ A Text-Book of Inorganic Chemistry. Forgotten Books. ISBN 978-1-4510-0469-4.
- ^ Aterton Seidell (1940). Solubilities Of Organic Compounds Vol - I. Carnegie-Mellon University Hunt Library, N.Sathyanarayanan. D.Van Nostrand Co.
- ^ a b c Dickerson, Richard E. (1988). Prinzipien der Chemie (in German). Walter de Gruyter. ISBN 978-3-11-009969-0.
- ^ texte, Académie des sciences (France) Auteur du (1911-01-01). "Comptes rendus hebdomadaires des séances de l'Académie des sciences / publiés... par MM. les secrétaires perpétuels". Gallica. Retrieved 2023-12-24.
- "Rubidium compounds: rubidium fluoride". WebElements: the periodic table on the web. WebElements. Retrieved 16 November 2011.
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