What is the chemical formula of hydrochloric acid?

Hydrochloric acid is a strong acid composed of hydrogen and chlorine. The chemical formula for hydrochloric acid is represented as HCl, which denotes that each molecule of hydrochloric acid consists of one hydrogen (H) atom bonded to one chlorine (Cl) atom. This simple structure makes it a diatomic molecule, and its acidity is due to the ability of the hydrogen ion (H⁺) to dissociate and contribute to the acidic properties in aqueous solutions.

The other compounds listed in the choices serve different purposes: H2O is the chemical formula for water, a vital substance for all known forms of life; NaCl is the formula for sodium chloride, commonly known as table salt; and CH3COOH is acetic acid, a weaker organic acid found in vinegar. Therefore, the correct choice accurately identifies hydrochloric acid, which is essential in various chemical reactions and processes.