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Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colorless, acidic and highly corrosive . A common concentration is 49% (48-52%) but there are also stronger solutions (e.g. 70%) and pure HF has a boiling point near room temperature.
Aqueous solutions of HF are called hydrofluoric acid. When dilute, hydrofluoric acid behaves like a weak acid, unlike the other hydrohalic acids, due to the formation of hydrogen-bonded ion pairs [H 3 O + ·F −]. However concentrated solutions are strong acids, because bifluoride anions are predominant, instead of ion pairs.
Hydrofluoric acid is a weak acid in aqueous solution (pK a = 3.15) [7] but a very weak acid in the gas phase (E pa (F −) = 1554 kJ/mol): [4] the fluoride ion is as strong a base as SiH 3 − in the gas phase, but its basicity is reduced in aqueous solution because it is strongly hydrated, and therefore stabilized.
Unlike other hydrohalic acids, such as hydrochloric acid, hydrogen fluoride is only a weak acid in water solution, with acid dissociation constant (pK a) equal to 3.19. [36] HF's weakness as an aqueous acid is paradoxical considering how polar the HF bond is, much more so than the bond in HCl, HBr, or HI. The explanation for the behavior is ...
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, also known as sodium chloride (NaCl), in water would be represented as Na + (aq) + Cl − (aq). The word aqueous (which comes from aqua) means ...
This neutralization reaction forms hydrogen fluoride (HF), the conjugate acid of fluoride. In aqueous solution, fluoride has a pK b value of 10.8. It is therefore a weak base, and tends to remain as the fluoride ion rather than generating a substantial amount of hydrogen fluoride. That is, the following equilibrium favours the left-hand side in ...
Subunit of crystal structure of [H 3 O] + [BF 4] − highlighting the hydrogen bonding between the cation and the anion. Aqueous solutions of H[BF 4] are produced by dissolving boric acid in aqueous hydrofluoric acid. [8] [9] Three equivalents of HF react to give the intermediate boron trifluoride and the fourth gives fluoroboric acid:
Hydrogen fluoride, a weak acid in aqueous solution that is normally not thought to have any appreciable Brønsted basicity at all, is in fact the strongest Brønsted base in the mixture, protonating to H 2 F + in the same way water protonates to H 3 O + in aqueous acid. It is the fluoronium ion that accounts for fluoroantimonic acid's extreme ...