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Ammonium bifluoride, as its name indicates, contains an ammonium cation ([NH 4] +), and a bifluoride (or hydrogen difluoride) anion ([HF 2] −).The triatomic bifluoride anion features a strong three-center four-electron bond (specifically, a symmetrical hydrogen bond) with a bond energy greater than 155 kJ/mol, [2] and an H-F length of 114 pm. [3]
Ammonium fluoride is a critical component of buffered oxide etch (BOE), a wet etchant used in microfabrication. It acts as the buffering agent in a solution of concentrated HF , creating an etchant with a more controllable rate of etching (than that of simple concentrated HF solutions).
Because the fluoride ion is such a strong hydrogen bond acceptor, its salts tend to be hydrated and of limited solubility in organic solvents. As a fluoride ion source, TBAF solves this problem, although the nature of the fluoride is uncertain because TBAF samples are almost always hydrated, resulting in the formation of bifluoride (HF 2 −) hydroxide (OH −) as well as fluoride.
Hydrogen fluoride is typically produced by the reaction between sulfuric acid and pure grades of the mineral fluorite: [14] CaF 2 + H 2 SO 4 → 2 HF + CaSO 4 About 20% of manufactured HF is a byproduct of fertilizer production, which generates hexafluorosilicic acid .
The Sb–F bonds are 2.02 Å within the eight-membered Sb 4 F 4 ring; the remaining fluoride ligands radiating from the four Sb centers are shorter at 1.82 Å. [7] The related species PF 5 and AsF 5 are monomeric in the solid and liquid states, probably due to the smaller sizes of the central atom, which limits their coordination number.
Buffered oxide etch (BOE), also known as buffered HF or BHF, is a wet etchant used in microfabrication.It is a mixture of a buffering agent, such as ammonium fluoride NH 4 F, and hydrofluoric acid (HF).
Sodium bifluoride is the inorganic compound with the formula Na[HF 2].It is a salt of sodium cation (Na +) and bifluoride anion ([HF 2] −).It is a white, water-soluble solid that decomposes upon heating . [2]
Because the fluoride anion is highly basic, many alkali metal fluorides form bifluorides with the formula MHF 2. Sodium and potassium bifluorides are significant to the chemical industry. [2] Among other monofluorides, only silver(I) [3] and thallium(I) [4] fluorides are well-characterized. Both are very soluble, unlike the other halides of ...