What is the common name for HCl?

The common name for HCl is hydrochloric acid. This nomenclature is derived from the way the compound is formed and how it behaves in an aqueous solution.

In aqueous solutions, HCl dissociates into hydrogen ions (H⁺) and chloride ions (Cl⁻). The term "hydrochloric acid" is used to indicate this aqueous solution, reflecting the acid's composition: it contains the hydrogen ion (indicating acidity) and the chloride ion (from the chlorine element). This naming convention is consistent with how other binary acids are named, especially those that consist of hydrogen and a single non-metal, where the prefix "hydro-" denotes the presence of hydrogen, and the suffix "-ic" is added based on the non-metal species involved.

In contrast, other options present compounds that do not correspond to HCl or commonly used names for HCl. Hydrosulfuric acid pertains to H₂S, hydrogen chloride refers to the gaseous form of HCl rather than its acid form, and hydrofluoric acid refers specifically to HF, which contains fluorine. Thus, hydrochloric acid is the widely accepted name used in both laboratory and industrial contexts for HCl when it is in an aqueous solution.