Which pH number is most indicative of a strong acid?

The pH scale ranges from 0 to 14, with lower values indicating increasing acidity and higher values indicating increasing alkalinity. A pH of 7 is considered neutral. When evaluating the strength of an acid, a lower pH value indicates a stronger acid.

In this context, a pH of 1 is very low, suggesting a high concentration of hydrogen ions (H⁺), which is characteristic of strong acids, such as hydrochloric acid. Strong acids dissociate completely in water, contributing significantly to the hydrogen ion concentration, which is reflected in the low pH value.

Other choices fall into higher ranges on the pH scale, suggesting weaker acids or neutral conditions. A pH of 5 or 6, while still acidic, does not indicate the same level of acidity as a pH of 1, which is characteristic of a strong acid.