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Hydrogen fluoride

Hydrogen fluoride
Hydrogen fluoride.svg
Hydrogen-fluoride-2D-dimensions.png
Hydrogen-fluoride-3D-vdW.png
Identifiers
7664-39-3 YesY
3D model (Jmol) Interactive image
ChEBI CHEBI:29228 YesY
ChemSpider 14214 YesY
ECHA InfoCard 100.028.759
KEGG C16487 YesY
PubChem 16211014
RTECS number MW7875000
UNII RGL5YE86CZ YesY
Properties
FH
Molar mass 20.01 g·mol−1
Appearance colourless gas or colourless liquid (below 19.5°C)
Density 1.15 g/L, gas (25 °C)
0.99 g/mL, liquid (19.5 °C)
Melting point −83.6 °C (−118.5 °F; 189.6 K)
Boiling point 19.5 °C (67.1 °F; 292.6 K)
miscible
Vapor pressure 783 mmHg (20 °C)
Acidity (pKa) 3.17
1.00001
Structure
Linear
1.86 D
Thermochemistry
8.687 J/g K (gas)
−13.66 kJ/g (gas)
−14.99 kJ/g (liquid)
Hazards
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 4: Very short exposure could cause death or major residual injury. E.g., VX gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Lethal dose or concentration (LD, LC):
1276 ppm (rat, 1 hr)
1774 ppm (monkey, 1 hr)
4327 ppm (guinea pig, 15 min)
313 ppm (rabbit, 7 hr)
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 3 ppm
REL (Recommended)
TWA 3 ppm (2.5 mg/m3) C 6 ppm (5 mg/m3) [15-minute]
IDLH (Immediate danger)
30 ppm
Related compounds
Other anions
Hydrogen chloride
Hydrogen bromide
Hydrogen iodide
Hydrogen astatide
Other cations
Sodium fluoride
Potassium fluoride
Rubidium fluoride
Caesium fluoride
Related compounds
Water
Ammonia
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY  (what is YesYN ?)
Infobox references

Hydrogen fluoride is a chemical compound with the chemical formula HF. This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It thus is the precursor to many important compounds including pharmaceuticals and polymers (e.g. Teflon). HF is widely used in the petrochemical industry as a component of superacids. Hydrogen fluoride boils near room temperature, much higher than other hydrogen halides. Unlike other hydrogen halides, HF is lighter than air.

Hydrogen fluoride is a highly dangerous gas, forming corrosive and penetrating hydrofluoric acid upon contact with moisture. The gas can also cause blindness by rapid destruction of the corneas.

French chemist Edmond Frémy (1814–1894) is credited with discovering anhydrous hydrogen fluoride while trying to isolate fluorine, although Carl Wilhelm Scheele prepared hydrofluoric acid in large quantities in 1771, and this acid was known in the glass industry before then.

Although a diatomic molecule, HF forms relatively strong intermolecular hydrogen bonds. Solid HF consists of zigzag chains of HF molecules. The HF molecules, with a short H–F bond of 95 pm, are linked to neighboring molecules by intermolecular H–F distances of 155 pm. Liquid HF also consists of chains of HF molecules, but the chains are shorter, consisting on average of only five or six molecules.

Hydrogen fluoride does not boil until 20 °C in contrast to the heavier hydrogen halides which boil between −85 °C (−120 °F) and −35 °C (−30 °F). This hydrogen bonding between HF molecules gives rise to high viscosity in the liquid phase and lower than expected pressure in the gas phase.


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Wikipedia

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