PH

pH is a measure of the activity of hydrogen ions (H+) in a solution and, therefore, its acidity or alkalinity. In aqueous systems, the hydrogen ion activity is dictated by the dissociation constant of water (Kw) = 1.011 × 10−14 at 25 °C) and interactions with other ions in solution. Due to this dissociation constant a neutral solution (hydrogen ion activity equals hydroxide ion activity) has a pH of approximately 7. Aqueous solutions with pH values lower than 7 are considered acidic, while pH values higher than 7 are considered alkaline.

Related Topics:
Activity - Hydrogen - Ion - Solution - Acidity - Alkalinity - Aqueous - Dissociation constant

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The concept was introduced by S.P.L. Sørensen in 1909. The p stands for the German Potenz, meaning power or potency, and the H for the hydrogen ion (H+). Sometimes it is referred as Latin pondus hydrogenii.

Related Topics:
S.P.L. Sørensen - 1909 - German - Hydrogen - Latin

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