ACS Chemistry Practice Exam 2025 – The All-in-One Guide to Exam Success!

Hydrogen iodide is the correct common name for HI. This chemical compound consists of hydrogen (H) and iodine (I) atoms. In the context of nomenclature and common naming conventions, the prefix "hydrogen" denotes the presence of the hydrogen element, while "iodide" indicates that iodine is in a monoatomic form with a negative charge.

The formula HI represents the simplest binary hydrogen halide, where hydrogen combines with iodine. In aqueous solutions, hydrogen iodide behaves as a strong acid, often referred to as hydroiodic acid. This understanding of the molecular composition is key to identifying its common name.

The other options refer to different compounds entirely, which have distinct names and compositions. Hydrochloric acid, for instance, is HCl, and hydrogen bromide is HBr, which are different halides. Chloric acid is a completely different substance altogether, represented by HClO3 and containing chlorine and oxygen, not iodine. Therefore, understanding the constituent elements and the naming conventions leads directly to recognizing HI as hydrogen iodide.