Final answer:
When hydrogen fluoride (HF) dissolves in water, it becomes hydrofluoric acid as it dissociates into fluoride anions and hydronium ions, forming an equilibrium between the dissociated and undissociated HF. The aqueous solution is denoted as HF(aq).
Step-by-step explanation:
When molecular hydrogen fluoride (HF) is dissolved in water, it forms hydrofluoric acid. This process involves water molecules orienting around the HF molecule and forming hydrogen bonds with the hydrogen atom, causing the H-F bond to stretch and eventually break. The result of this bond dissociation is the formation of two ions: a fluoride anion (F-) and a hydronium ion (H3O+), which is essential to the definition of an acid in water. The dissociation of HF in water can be represented as an equilibrium, where the forward reaction is HF dissociating into H+ and F-, and the reverse being H+ combining with F- to reform HF.
Accordingly, the proper name for HF when it is dissolved in water is hydrofluoric acid (HF(aq)). This nomenclature is consistent with other acids such as hydrochloric acid from hydrogen chloride (HCl) and hydrosulfuric acid from hydrogen sulfide (H2S). The aqueous solution (aq) denotes that HF is dissolved in water, indicating that it has dissociated to some extent into its ionic components, contributing to the acidity of the solution.