Hexafluorophosphoric acid

{{chembox

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 428735313

| Reference =

{{Cite book| last = Lide| first = David R.| year = 1998| title = Handbook of Chemistry and Physics| edition = 87| location = Boca Raton, FL| publisher = CRC Press| isbn = 0-8493-0594-2| pages = 4–74}}

| ImageFile = Hexafluorophosphoric acid.svg

| ImageFileL1 = Hydronium-3D-vdW.svg

| ImageCaptionL1 = Oxonium ion

| ImageFileR1 = Hexafluorophosphate-anion-3D-vdW.png

| ImageCaptionR1 = Hexafluorophosphate ion

| IUPACName = Hexafluorophosphoric acid{{cite web|url=https://moam.info/nomenclature-of-inorganic-chemistry-iupac_59c16afb1723ddd2fb171db1.html|title=Nomenclature of Inorganic Chemistry|last=IUPAC|access-date=2021-04-08}}

| OtherNames = Hydrogen hexafluorophosphate
Hydron hexafluorophosphate

| Section1 = {{Chembox Identifiers

| PubChem = 16211447

| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}

| ChemSpiderID = 17339451

| SMILES = [H+].F[P-](F)(F)(F)(F)F

| InChI = 1/F6P/c1-7(2,3,4,5)6/q-1/p+1

| InChIKey = LJQLCJWAZJINEB-IKLDFBCSAL

| StdInChI_Ref = {{stdinchicite|changed|chemspider}}

| StdInChI = 1S/F6P/c1-7(2,3,4,5)6/q-1/p+1

| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}

| StdInChIKey = LJQLCJWAZJINEB-UHFFFAOYSA-O

| EINECS = 241-006-5

| CASNo_Ref = {{cascite|correct|??}}

| CASNo = 16940-81-1

}}

| Section2 = {{Chembox Properties

| Formula = HPF₆

| MolarMass = 145.972 g/mol

| Appearance = colorless oily liquid

| Solubility = exists only in solution

| MeltingPt = decomposes at 25 °C

}}

| Section7 = {{Chembox Hazards

| MainHazards = Corrosive

| GHSPictograms = {{GHS05}}{{GHS06}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|301|311|314|330}}

| PPhrases = {{P-phrases|260|264|271|280|284|301+330+331|303+361+353|304+340|305+351+338|310|320|321|363|403+233|405|501}}

}}

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Hexafluorophosphoric acid refers to a family of salts produced by combining phosphorus pentafluoride and hydrofluoric acid. The idealized chemical formula for hexafluorophosphoric acid

is {{chem2|HPF6}}, which also is written {{chem2|H[PF6]}}.{{cite book

| title = Superacid Chemistry

| author = Arpad Molnar

| author2 = G. K. Surya Prakash

| author3 = Jean Sommer

| edition = 2nd

| publisher = Wiley-Interscience

| year = 2009

| isbn = 978-0-471-59668-4

| page = 44

}} Hexafluorophosphoric acid is only stable in solution, decomposing to HF and PF₅ when dry.{{Kirk-Othmer|doi=10.1002/0471238961.1608151912091404.a01|title=Fluorine compounds, inorganic, phosphorus|first1=Charles B.|last1=Lindahl|first2=Tariq|last2=Mahmood|year=2000}} It exothermically reacts with water to produce oxonium hexafluorophosphate ({{chem2|[H3O]+[PF6]-}}) and hydrofluoric acid. Additionally, such solutions often contain products derived from hydrolysis of the P-F bonds, including {{chem2|HPO2F2}}, {{chem2|H2PO3F}}, and {{chem2|H3PO4}}, and their conjugate bases.{{cite journal

| doi = 10.1139/v72-565

| author = D. W. Davidson

| author2 = S. K. Garg

| journal = Canadian Journal of Chemistry

| date=May 1972

| title = The Hydrate of Hexafluorophosphoric Acid

| volume = 50

| issue = 21

| pages = 3515–3520

| doi-access = free

}} Hexafluorophosphoric acid attacks glass. Upon heating, it decomposes to generate HF. Crystalline {{chem|HPF|6}} has been obtained as the hexahydrate, wherein {{chem|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.

Whereas a species with the formula HPF₆ remains unknown, the analogous molecular hexafluoroarsenic acid (HAsF₆) has been crystallized.{{cite journal |doi=10.1002/anie.201308023 |title=The Existence of Hexafluoroarsenic(V) Acid |year=2014 |last1=Axhausen |first1=Joachim |last2=Lux |first2=Karin |last3=Kornath |first3=Andreas |journal=Angewandte Chemie International Edition |volume=53 |issue=14 |pages=3720–3721 |pmid=24446235}}