Which of the following is considered a strong acid?

A strong acid is defined by its ability to completely dissociate in water, resulting in a high concentration of hydrogen ions (H⁺) in the solution. The pH scale ranges from 0 to 14, where lower values indicate higher acidity. A solution with a pH of 1 indicates a high concentration of hydrogen ions, which is characteristic of a strong acid. This very low pH level means that the solution can effectively donate protons, contributing to its classification as a strong acid.

In contrast, a pH of 7 is neutral, indicating a balance of hydrogen ions and hydroxide ions. A pH of 4, while acidic, is not as strong as a pH of 1, indicating a lower concentration of hydrogen ions. A pH of 10 is basic, meaning it has a greater concentration of hydroxide ions and lacks the characteristics of an acid altogether. Therefore, the pH of 1 is the only value among the options that qualifies as a strong acid.