Potassium bifluoride

Potassium bifluoride
IUPAC name

Potassium bifluoride
Other names

Potassium hydrogen difluoride
Identifiers
CAS number 7789-29-9
PubChem 11829350
ChemSpider 21241938 Y
RTECS number TS6650000
Jmol-3D images Image 1
Properties
Molecular formula HF2K
Molar mass 78.103 g/mol
Appearance colourless solid
Density 2.37 g/cm3
Melting point

239 °C
Boiling point

decomp.
Structure
Crystal structure monoclinic
Hazards
EU classification Toxic (T), Corrosive (C)
R-phrases R25-34
S-phrases S22-26, S37-45
Flash point non flammable
Related compounds
Other anions Potassium fluoride
Other cations Sodium bifluoride, ammonium bifluoride
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Potassium bifluoride is the inorganic compound with the formula KHF2. This colourless salt consists of the potassium cation and the bifluoride (HF2−) anion. The salt is used in etchant for glass. Sodium bifluoride is related and is also of commercial use as an etchant as well as in cleaning products.[1]

Contents

Nature of the chemical bond in the bifluoride anion

Potassium bifluoride, as its name indicates, contains a bifluoride, or hydrogen(difluoride) anion: HF2−. This centrosymmetric triatomic anion features the strongest known hydrogen bond, with a F−H length of 114 pm,[2] and a bond energy greater than 155 kJ mol−1.[3]

Synthesis and reactions

The salt was prepared by Edmond Frémy who decomposed it to generate, for the first time, hydrogen fluoride. Potassium bifluoride is prepared by treating potassium carbonate or potassium hydroxide with hydrofluoric acid:

2 HF + KOH → KHF2 + H2O

The electrolysis of KHF2 was used by Henri Moissan to isolate the element fluorine in 1886.

A related material containing two equivalents of HF is also known, KH2F3 (CAS#12178-06-2, m.p. 71.7 C). The industrial production of fluorine entails the electrolysis of molten KH2F3.[1]

See also

References

  1. ^ a b Jean Aigueperse, Paul Mollard, Didier Devilliers, Marius Chemla, Robert Faron, Renée Romano, Jean Pierre Cuer, “Fluorine Compounds, Inorganic” in Ullmann’s Encyclopedia of Industrial Chemistry 2005 Wiley-VCH, Weinheim. doi:10.1002/14356007.a11 307
  2. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419. 
  3. ^ Emsley, J. (1980) Very strong hydrogen bonds, Chemical Society Reviews, 9, 91-124.