Final answer:
HBr is a strong acid because it ionizes completely in water, dissociating into hydrogen and bromide ions.
Step-by-step explanation:
HBr, or hydrogen bromide, is classified as a strong acid. In aqueous solutions, HBr ionizes completely into hydrogen (H+) ions and bromide (Br−) ions. This full ionization is characteristic of a strong acid, as opposed to a weak acid, which only partially dissociates in water. Acids like acetic acid (HC2H3O2), which do not fully dissociate, are examples of weak acids and tend to have reversible reactions demonstrating partial ionization. In contrast, strong acids such as HBr and HCl have essentially irreversible dissociations, indicating that they donate hydrogen ions readily in solution.