Hexafluorophosphoric acid is the inorganic compound with the chemical formula HPF
6 (also written H[PF
6]). This strong Brønsted acid features a non-coordinating anion, hexafluorophosphate (PF−
6). It is formed from the reaction of hydrogen fluoride with phosphorus pentafluoride.
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||145.972 g/mol|
|Appearance||colorless oily liquid|
|Melting point||decomposes at 25 °C|
|exists only in solution|
|Occupational safety and health (OHS/OSH):|
|H301, H311, H314, H330|
|P260, P264, P271, P280, P284, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P320, P321, P363, P403+P233, P405, P501|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
(what is ?)
Like many strong acids, hexafluorophosphoric acid is not isolable but is handled only in solution. It exothermically reacts with water to produce oxonium hexafluorophosphate (H
6) and hydrofluoric acid. Additionally, such solutions often contain products derived from hydrolysis of the P-F bonds, including HPO
2F, and H
4, and their conjugate bases. Hexafluorophosphoric acid attacks glass. Upon heating, it decomposes to generate HF. Crystalline HPF
6 has been obtained as the hexahydrate, wherein PF−
6 is enclosed in truncated octahedral cages defined by the water and protons. NMR spectroscopy indicates that solutions derived from this hexahydrate contain significant amounts of HF.