What is the pH of a neutral solution at 25°C?

The pH of a neutral solution at 25°C is defined as 7. This value arises from the autoionization of water, where water molecules dissociate into hydronium (H₃O⁺) and hydroxide (OH⁻) ions. In pure water, the concentration of H₃O⁺ ions equals that of OH⁻ ions, each being 1.0 x 10⁻⁷ mol/L at 25°C.

The pH is calculated using the formula pH = -log[H₃O⁺]. When you substitute the neutral concentration of H₃O⁺ (1.0 x 10⁻⁷ M) into this equation, the pH comes out to be 7. This neutral point indicates neither acidic nor basic characteristics, which is vital for understanding acid-base chemistry.

The other values—5, 6, and 8—do not represent the neutral condition at this temperature. A pH of 5 or 6 indicates an acidic solution, where the concentration of H₃O⁺ is higher than that of OH⁻, while a pH of 8 indicates a basic solution, where the concentration of