ALEKS Placement Chemistry Exam 2025 – 400 Free Practice Questions to Pass the Exam

The reasoning behind identifying as the option that is not a strong acid lies in its dissociation behavior in water. Strong acids are defined by their ability to completely dissociate into their ions when dissolved in water, thereby contributing a high concentration of hydrogen ions (H⁺) to the solution.

Hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and nitric acid (HNO₃) are all examples of strong acids because they completely dissociate in aqueous solutions. This means that when any of these acids are added to water, they release all their available hydrogen ions, leading to a very low pH.

On the other hand, phosphoric acid (H₃PO₄) behaves differently. It is classified as a weak acid because it does not completely dissociate in solution. Instead, phosphoric acid has multiple ionizable hydrogen atoms, and only the first dissociation step is strong, while the subsequent steps are much weaker. As a result, in a typical solution, phosphoric acid does not lead to the same high concentration of hydrogen ions as the strong acids, emphasizing its classification as a weak acid.

Thus, H₃PO₄ stands out for its incomplete dissociation and consequently