Which pH level has the highest hydrogen ion concentration?

A pH level indicates how acidic or basic a solution is, measured on a logarithmic scale from 0 to 14. The scale represents hydrogen ion concentration, where lower pH values correspond to higher concentrations of hydrogen ions (H+).

In this context, a pH of 3 signifies a higher concentration of hydrogen ions compared to a pH of 4. Each decrease of one unit in pH signifies a tenfold increase in hydrogen ion concentration. Therefore, a solution with a pH of 3 has ten times more hydrogen ions than one with a pH of 4.

On the other hand, a pH level of 9 is basic, indicating a much lower concentration of hydrogen ions than those found at pH levels of 3 or 4. Similarly, a pH of 11 would represent an even lesser concentration of hydrogen ions compared to the previously mentioned pH values.

Thus, the pH of 3 has the highest hydrogen ion concentration among the options provided.