Which of the following is considered a strong acid?

Hydrochloric acid is classified as a strong acid because it completely dissociates in water, meaning that it ionizes entirely to release hydrogen ions (H⁺) and chloride ions (Cl⁻). This characteristic allows hydrochloric acid to effectively lower the pH of a solution, making it highly effective in various chemical reactions, particularly in digestion and laboratory settings.

On the other hand, acetic acid, citric acid, and carbonic acid are considered weak acids because they do not fully dissociate in solution. Acetic acid only partially ionizes, meaning that not all of its molecules release H⁺ ions. Similarly, citric acid and carbonic acid also exhibit incomplete dissociation. This distinction is crucial in acid-base chemistry as it defines the acid's strength and its behavior in different chemical environments.