What describes a substance that is completely ionized in its solution and has a pH of 2?

A substance that is completely ionized in its solution and has a pH of 2 is best described as a strong acid. Strong acids, such as hydrochloric acid or sulfuric acid, dissociate fully in water, meaning that they release all of their hydrogen ions (H⁺) into the solution. The pH scale is a measure of the concentration of hydrogen ions in a solution, with lower pH values indicating a higher concentration of H⁺ ions.

A pH of 2 indicates a high concentration of hydrogen ions, which aligns with the behavior of strong acids. In contrast, strong bases would have a high pH (greater than 7) due to a high concentration of hydroxide ions (OH⁻). Weak acids and weak bases, on the other hand, only partially ionize in solution, leading to higher pH values than that of a strong acid at the same concentration. Therefore, the characteristics of complete ionization and a low pH distinctly identify the substance as a strong acid.