Advanced Placement (AP) Chemistry Practice Exam

Strong acids are characterized by which of the following properties?

1. They partially dissociate in water.

2. They do not dissociate in water.

3. They dissociate completely in water.

4. They are usually weak electrolytes.

The correct answer is: They dissociate completely in water.

Strong acids are defined by their ability to dissociate completely in aqueous solutions. When a strong acid is added to water, it breaks apart into its constituent ions fully, meaning that virtually all of the acid molecules donate protons (H⁺ ions) to water. This complete ionization leads to a high concentration of H⁺ ions in solution, which correlates with a low pH characteristic of strong acids. In contrast to strong acids, weak acids only partially dissociate, resulting in an equilibrium between the undissociated acid and the ions in solution. Therefore, the other properties listed do not apply to strong acids. In summary, the complete dissociation of strong acids in water is what fundamentally characterizes their behavior in aqueous solutions.