Difference between revisions of "Potassium bifluoride"
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[[Category:Fluorides]] | [[Category:Fluorides]] | ||
[[Category:Bifluorides]] | [[Category:Bifluorides]] | ||
Latest revision as of 17:35, 26 August 2025
| Names | |
|---|---|
| IUPAC name
Potassium hydrogen difluoride
| |
| Other names
Potassium hydrogen bifluoride
| |
| Properties | |
| KHF2 or K[HF2] | |
| Molar mass | 78.103 g/mol |
| Appearance | White crystalline solid |
| Odor | Slightly acidic |
| Density | 2.37 g/cm3 |
| Melting point | 238.7 °C (461.7 °F; 511.8 K) |
| Boiling point | Decomposes |
| 24.5 g/(100 ml) (0 °C) 30.1 g/(100 ml) (10 °C) 39.2 g/(100 ml) (20 °C) 114.0 g/(100 ml) (80 °C) | |
| Solubility | Soluble in ethanol |
| Vapor pressure | ~0 mmHg |
| Hazards | |
| Flash point | Non-flammable |
| Related compounds | |
| Related compounds
|
Ammonium bifluoride Sodium bifluoride |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Potassium bifluoride is a salt with the formula KHF2. It is a white crystalline solid, hygroscopic, and has slight acidic odour to it.
Contents
Properties
Chemical
When added to an acidic solution, potassium bifluoride releases hydrogen fluoride which is a highly corrosive and dangerous gas.
- K[HF2] + H+ → HF + KF + H+
Electrolysis of potassium bifluoride produces elemental fluorine.[1]
- 2 KHF2(l) → 2 KF(l) + H2(g) + F2(g)
Physical
Potassium bifluoride (KHF2) is a white, crystalline solid that is highly soluble in water. It has a melting point of 238.7 °C and decomposes before boiling. KHF2 is acidic in its solution due to the release of hydrofluoric acid upon hydrolysis.
Availability
Potassium bifluoride can be purchased from glass manufacturers and chemical companies.
Preparation
Reaction of anhydrous hydrogen fluoride with potassium hydroxide yields potassium bifluoride. Concentrated hydrofluoric acid can also be reacted with potassium hydroxide to produce potassium bifluoride but an extra purification step is required to remove potassium fluoride formed as a reaction product.
Projects
- Make elemental fluorine
- Etching glass
Handling
Safety
Potassium bifluoride should be handled carefully with gloves and a suitable respirator as this substance is quite irritating to the nose and the skin. If ingested fluoride ions can become quite poisonous. Potassium bifluoride should not be heated above its melting point as this may lead to decomposition of the salt and formation of highly corrosive hydrogen fluoride gas and potassium fluoride.
Storage
Potassium bifluoride should be stored in an airtight container (preferably a desiccator) since it's hygroscopic. As it may release HF fumes and fluorides are corrosive to glass, a plastic container (and a desiccator) should be used.
Disposal
Potassium bifluoride should not be poured down the drain because fluoride ions at higher concentrations are quite toxic for the environment. It can be recycled for fluoride ions or should be given to a specific authority for its safe disposal. Alternatively, it can be mixed with a solution of calcium salts, which will yield the insoluble and non-toxic calcium fluoride. The reaction of soluble calcium salts with the released fluoride ions from Potassium bifluoride in an aqueous solution can be given as
- Ca2+ + 2F- → CaF2↓
