Which type of acid is characterized by completely ionizing in a solution?

A strong acid is characterized by its ability to completely ionize in a solution, meaning that when it is dissolved in water, it dissociates completely into its ions. This results in a high concentration of hydrogen ions (H+) in the solution, which is why strong acids exhibit a low pH and can lead to highly reactive solutions.

Examples of strong acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3). The defining feature of these acids is their complete dissociation; for instance, when HCl is added to water, it fully separates into H+ and Cl- ions, leaving no undissociated HCl molecules in the solution.

In contrast, weak acids only partially ionize in a solution, meaning that not all of the acid molecules will dissociate into ions. This results in a mixture of ionized and un-ionized forms in the solution. Organic acids, which can be either weak or strong, often do not fully dissociate, further distinguishing them from strong acids. Therefore, the characteristic of complete ionization in solution confirms that the correct answer is strong acid.