Rubidium fluoride
Chemical compound
From Wikipedia, the free encyclopedia
Rubidium fluoride (RbF) is the fluoride salt of rubidium. It is a white crystalline solid with a cubic crystal structure, similar to common salt. It forms two different hydrates, a sesquihydrate with the stoichiometric composition 2RbF·3H2O and a third hydrate with the composition 3RbF·H2O.[5]
| |
| Names | |
|---|---|
| Other names
Rubidium(I) Fluoride | |
| Identifiers | |
3D model (JSmol) |
|
| ChemSpider | |
| ECHA InfoCard | 100.033.262 |
PubChem CID |
|
| RTECS number |
|
| UNII | |
CompTox Dashboard (EPA) |
|
| |
| |
| Properties | |
| 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) |
| 130.6 g/100 mL (18 °C) | |
| Solubility in acetone | 0.0036 g/kg (18 °C)[1] 0.0039 g/kg (37 °C)[1] |
| −31.9·10−6 cm3/mol | |
Refractive index (nD) |
1.398[2] |
| Structure[2] | |
| Fm3m (No. 225) | |
a = 565 pm | |
Formula units (Z) |
4 |
| Thermochemistry[3] | |
Std molar entropy (S⦵298) |
113.9 J·mol-1·K-1 |
Std enthalpy of formation (ΔfH⦵298) |
−552.2 kJ/mol |
Gibbs free energy (ΔfG⦵) |
−520.4 kJ/mol |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards |
Toxic |
| GHS labelling:[4] | |
   | |
| Danger | |
| H301, H302, H311, H312, H315, H319, H331, H332, H335, H351 | |
| P203, P261, P262, P264, P264+P265, P270, P271, P280, P301+P316, P301+P317, P302+P352, P304+P340, P305+P351+P338, P316, P317, P318, P319, P321, P330, P332+P317, P337+P317, P361+P364, P362+P364, P403+P233, P405, P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
Threshold limit value (TLV) |
2.5 mg/m3, as F |
| NIOSH (US health exposure limits): | |
PEL (Permissible) |
2.5 mg/m3, as F |
| 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).
| |
Synthesis
There are several methods for synthesising rubidium fluoride. One involves reacting rubidium hydroxide with hydrofluoric acid:[6]
- RbOH + HF → RbF + H2O
Another method is to neutralize rubidium carbonate with hydrofluoric acid:[6]
- 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:[6]
- 2Rb + F2 → 2RbF
Properties
The enthalpy of solution of rubidium fluoride was determined to be −24.28 kJ/mol.[7]
Rubidium fluoride has a purple or magenta red flame test.