Hydrogen fluoride

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 is an important feedstock in the preparation of 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. 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 is an important feedstock in the preparation of 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. 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. In 1771 Carl Wilhelm Scheele prepared the aqueous solution, hydrofluoric acid in large quantities, although hydrofluoric acid had been known in the glass industry before then.French chemist Edmond Frémy (1814–1894) is credited with discovering anhydrous hydrogen fluoride (HF) while trying to isolate fluorine. Although a diatomic molecule, HF forms relatively strong intermolecular hydrogen bonds. Solid HF consists of zig-zag 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. HF is miscible with water (dissolves in any proportion). In contrast, the other hydrogen halides exhibit limiting solubilities in water. Hydrogen fluoride form a monohydrate HF.H2O (−40 °C (−40 °F), which is 44 °C (79 °F) above the melting point of pure HF. Aqueous solutions of HF are called hydrofluoric acid. When dilute, hydrofluoric acid is a weak acid, unlike the other hydrohalic acids. However concentrated solutions are strong acids due to the formation of hydrogen-bonded ion pairs . In liquid anhydrous HF, self-ionization occurs: which forms an extremely acidic solution (H0 = −11). HF reacts with Lewis acids to give superacids. H0 of −21 result with SbF5.