The pH of a solution depends on both the concentration of hydrogen ions (H+) and the temperature of the solution. At a given temperature, the pH is inversely proportional to the concentration of hydrogen ions. In other words, the higher the concentration of hydrogen ions, the lower the pH.

Temperature can also affect the pH of a solution. In general, the pH of a solution decreases with increasing temperature. This is because the rate of dissociation of water molecules increases with increasing temperature, which leads to a higher concentration of hydrogen ions in the solution.

The concentration of other compounds in the solution can also affect the pH. For example, the presence of strong acids or bases can significantly alter the pH of the solution.

For a given compound, there's a specific concentration at which the pH of the solution shows a noticeable change. In the context of weak acids and bases, this specific concentration usually corresponds to the compound's pKa or pKb value, respectively.