What is the pH of a neutral solution at 25 degrees Celsius?

A neutral solution, such as pure water at 25 degrees Celsius, has a pH value of 7. At this temperature, the concentrations of hydrogen ions (H⁺) and hydroxide ions (OH⁻) are equal, resulting in a balanced state where neither acidic nor basic properties dominate. The pH scale is logarithmic; it runs from 0 to 14, where lower values indicate acidity, higher values indicate basicity, and a pH of 7 is designated as neutral.

The concept of neutrality is specifically connected to the auto-ionization of water, where water molecules dissociate into H⁺ and OH⁻ ions in equal amounts. Since at 25 degrees Celsius the concentration of hydrogen ions is 1 × 10⁻⁷ M, this leads to a pH of 7, which signifies that the solution is neither acidic nor basic.

In the context of pH values, a pH of 0 would indicate a highly acidic solution, and a pH of 14 would indicate a highly basic solution. A pH of 10, while above neutral, is still considered basic. Thus, 7 is the definitive pH for neutrality at this temperature.