For 10 points, name this unstable lightest hydrogen halide.
One synthesis of this compound results in product loss through a side reaction with SiO2 and involves adding sulfuric acid to a form of apatite. As a liquid, this compound coexists as a long zig-zag chain with x monomers and as a hexameric puckered six member ring. Linear alkyl benzene formation is catalyzed by the addition of aluminum chloride and this compound. This compound can remove impurities from stainless steel in a process known as pickling. A 1:1 mixture of this compound and one containing (*) antimony in the 5+ oxidation state is the strongest known superacid. It forms the HNA mixture with nitric and acetic acid. Chloroform and this compound are used in Teflon synthesis. It is used to etch glass. For 10 points, name this unstable lightest hydrogen halide.
One synthesis of this compound results in product loss through a side reaction with SiO2 and involves adding sulfuric acid to a form of apatite.
hydrogen fluoride [or HF; or hydrofluoric acid]