Final answer:
The IUPAC name for HCN(aq) is hydrocyanic acid, following the naming convention for acids where 'hydro-' is prefixed to the anion name and '-ide' becomes '-ic acid'.
Step-by-step explanation:
The correct IUPAC name for HCN(aq) is hydrocyanic acid. This naming convention is used when the compound acts as an acid, particularly when it is in aqueous solution (aq) form. If HCN were not in solution or not acting as an acid, it would be named hydrogen cyanide, but since it is in solution and can donate a proton (H+), the acid naming convention applies.
Naming as acids involves adding the prefix hydro- to the name of the anion, and replacing the last syllable from -ide to -ic acid. This rule applies to other acids as well, such as HCl being named hydrochloric acid, and HI being named hydroiodic acid. In the context of equilibrium and reactions, hydrocyanic acid can participate in reactions such as its neutralization with potassium hydroxide (KOH(aq)), forming a salt.