Hydrogen fluoride
3352423
221574471
2008-06-25T03:13:55Z
71.113.6.147
/* Uses */
{| class="chembox" border="1" style="float: right; clear: right; margin: 0 0 1em 1em; border-collapse: collapse;"
! align="center" cellspacing="3" style="border: 1px solid #C0C090; background-color: #F8EABA; margin-bottom: 3px;" colspan="2" | Hydrogen fluoride
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| align="center" colspan="2" bgcolor="#ffffff" | [[Image:Hydrogen-fluoride-2D-dimensions.png|120px|Hydrogen fluoride molecule]] [[Image:Hydrogen-fluoride-3D-vdW.png|120px|Hydrogen fluoride molecule]]<br>[[Image:Hydrogen-fluoride-solid-chains-3D-vdW.png|260px|Hydrogen fluoride chains in the solid phase]]
|-
<!--- | [[IUPAC name|Systematic name]]
| {{{Systematic name}}} --->
|-
| Other names
| Hydrogen fluoride<br>Fluoric acid<br>Hydrofluoride<br>Hydrofluoric acid<br>Fluorine monohydride
|-
| [[Molecular formula]]
| HF
|-
| [[Molecular mass]]
| 20.01 g/mol
|-
| [[Physical state]]
| Liquid/Gas
|-
| [[CAS number]]
| 7664-39-3
|-
| [[Density]]
| 0.922 kg m<sup>-3</sup>
|-
| [[Solubility]] ([[Water (molecule)|water]])
| miscible
|-
| [[Melting point]]
| -84 °C (190 K, -118 °F)
|-
| [[Boiling point]]
| 19.54 °C (293 K, 67.2 °F)
|-
| [[NFPA 704]]
| {{NFPA 704 | Health=4 | Flammability = 0 | Reactivity = 2 }}
|-
| align="center" cellspacing="3" style="border: 1px solid #C0C090; background-color: #F8EABA; margin-bottom: 3px;" colspan="2" |<small>[[wikipedia:Chemical infobox|Disclaimer and references]]</small>
|-
|}
'''Hydrogen fluoride''' is a [[chemical compound]] with the [[chemical formula|formula]] HF. Together with [[hydrofluoric acid]], it is the principal industrial source of [[fluorine]] and hence the precursor to many important compounds including pharmaceuticals and polymers (e.g. [[Teflon]]). HF is widely used in the petrochemical industry and a component of many [[superacid]]s. HF boils just below room temperature whereas the other hydrogen [[halide]]s condense at much lower temperatures. Aqueous solutions of HF, called [[hydrofluoric acid]], are strongly corrosive.
==Structure==
[[Image:Hydrogen-fluoride-solid-2D-dimensions.png|left|400px|The structure of chains of HF in crystalline hydrogen fluoride.]]<br clear = left/>
HF forms orthorhombic crystals, consisting of zig-zag chains of HF molecules. The HF molecules, with a short H-F bond of 0.95 Å, are linked to neighboring molecules by intermolecular H--F distances of 1.55 Å.<ref>{{cite journal | author = Johnson, M. W.; Sándor, E.; Arzi, E. | title = The Crystal Structure of Deuterium Fluoride | journal = [[Acta Crystallographica]] | year = 1975 | volume = B31 | pages = pages 1998–2003 | doi = 10.1107/S0567740875006711}}</ref>
Liquid HF also consists of chains of HF molecules, but the chains are shorter, consisting on average of only five or six molecules.<ref>{{cite journal | title = On the Structure of Liquid Hydrogen Fluoride | journal = [[Angewandte Chemie]], International Edition | year = 2004 | volume = 43 | pages = 1952–55 | doi = 10.1002/anie.200353289 | author = Mclain, Sylvia E.}}</ref> The higher boiling point of HF relative to analogous species, such as HCl, is attributed to [[hydrogen bonding]] between HF molecules, as indicated by the existence of chains even in the liquid state.
==Acidity==
Dilute aqueous HF solutions are weakly acidic in contrast to corresponding solutions of the other hydrogen halides. A qualitative explanation for this behavior is related to the tendency of HF to hydrogen-bond and form ion-pair clusters such as F<sup>-</sup>·H<sub>3</sub>O<sup>+</sup>.<ref>{{cite journal
| doi = 10.1021/ja00537a008
| title = The nature of hydrofluoric acid. A spectroscopic study of the proton-transfer complex H<sub>3</sub>O<sup>+</sup>...F<sup>−</sup>
| year = 1980
| author = Giguere, Paul A.
| journal = [[J. Am. Chem. Soc.]]
| volume = 102
| pages = 5473}}</ref><ref>{{cite journal | author = Radu Iftimie, Vibin Thomas, Sylvain Plessis, Patrick Marchand, and Patrick Ayotte| title = Spectral Signatures and Molecular Origin of Acid Dissociation Intermediates | journal = [[J. Am. Chem. Soc.]] | doi = 10.1021/ja077846o| year = 2008| volume = 130| pages = 5901}}</ref>
In concentrated hydrogen fluoride solution, F<sup>−</sup> ions forms a [[hydrogen difluoride|[HF<sub>2</sub>]<sup>−</sup>]](aq) complex with HF molecules. HF molecules remaining ionize to compensate the loss of F<sup>−</sup> ions. More H<sup>+</sup> ions are thus formed, making concentrated HF an effectively strong acid.
Anhydrous hydrogen fluoride is an extremely strong acid ([[Hammett acidity function|''H''<sub>0</sub>]] ~ -11), comparable in strength to anhydrous [[sulfuric acid]] (''H''<sub>0</sub> ~ -12).
==Uses==
HF is used for fluorinating [[polymer]]s giving [[fluorocarbon]]s, [[petroleum refining]], glassmaking, [[aluminium]] manufacturing, [[titanium]] [[pickling (metal)|pickling]], [[quartz]] purification, and metal finishing. It is also used to synthesize [[uranium hexafluoride|UF<sub>6</sub>]], which is key to separating [[uranium]] [[isotope]]s.
Hydrogen fluoride can be found in consumer products for removing [[rust]], cleaning [[brass]], and glass [[industrial etching|etching]], although use in consumer products is discouraged {{Fact|date=February 2007}} due to HF's corrosiveness and [[toxicity]]. Hydrogen fluoride is typically marketed in three common forms: anhydrous HF, aqueous 70% HF, aqueous 49% HF. HF is manufactured by the reaction of [[calcium fluoride]] (fluorspar) and [[sulfuric acid]]:
:CaF<sub>2</sub> + H<sub>2</sub>SO<sub>4</sub> → CaSO<sub>4</sub> + 2 HF
The vapors from this reaction are a mixture of [[hydrogen fluoride]], [[sulfuric acid]], and a few minor byproducts.
== Health effects ==
{{Main|Hydrofluoric acid}}
Upon contact with moisture, including tissue, hydrogen fluoride immediately converts to [[hydrofluoric acid]], which is highly corrosive and toxic, and requires immediate medical attention.
== References==
<references/>
<div class="references-small">
*[http://www.atsdr.cdc.gov/MHMI/mmg11.html "[[ATSDR]] - MMG: Hydrogen Fluoride"]. Retrieved [[May 14]], [[2006]]
*Barbalace, Kenneth. [http://environmentalchemistry.com/yogi/chemicals/cn/Antimony%A0Pentafluoride.html "Chemical Database - Hydrogen Fluoride. EnvironmentalChemistry.com"]. 1995 - 2006. Retrieved [[May 14]], [[2006]]
* [http://www.honeywell.com/sites/sm/chemicals/hfacid/Anhydrous_HF.htm Honeywell, Industrial Fluorines G525-521, "Recommended Medical Treatment for Hydrofluoric Acid Exposure"]
*Cotton, F. A. and Wilkinson, G., ''Advanced Inorganic Chemistry'', John Wiley and Sons: New York, 1988. ISBN 0471849979
</div>
[[Category:Fluorides]]
[[Category:Hydrogen compounds]]
[[Category:Hazardous air pollutants]]
[[cs:Fluorovodík]]
[[de:Fluorwasserstoff]]
[[fr:Fluorure d'hydrogène]]
[[hu:Hidrogén-fluorid]]
[[ja:フッ化水素]]
[[no:Flussyre]]
[[nn:Flussyre]]
[[pl:Fluorowodór]]
[[ru:Фтороводород]]
[[sk:Fluorovodík]]
[[fi:Vetyfluoridi]]