Which type of acid is completely dissociated into its ions?

A strong acid is defined as an acid that completely dissociates into its ions when dissolved in water. This means that when a strong acid is added to water, it releases all of its hydrogen ions (H⁺) into the solution, resulting in a high concentration of H⁺ ions. This complete dissociation is a characteristic feature of strong acids, which include common acids such as hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and nitric acid (HNO₃).

In contrast, weak acids only partially dissociate in solution, meaning that not all of the acid molecules release their hydrogen ions. This results in a lower concentration of H⁺ ions compared to strong acids.

The term neutral acid typically refers to acids that are not strong or weak and may have a neutral effect on pH in very dilute solutions, but they do not characterize dissociation behavior.

Concentrated acid simply indicates the molarity or concentration of the acid solution but does not imply anything about its dissociation behavior. It is possible to have a concentrated weak acid that does not fully dissociate.

Thus, the characteristic of complete ion dissociation only applies to strong acids, affirming why a strong acid is the correct answer