pH is a logarithmic scale used to specify the acidity or basicity of an aqueous solution. It is defined as the negative logarithm of the hydrogen ion concentration: pH=−log[H+]
pH and Concentration
Each integer value on the pH scale represents a tenfold difference in hydrogen ion concentration
Measuring pH
pH can be measured using pH meters, which provide precise readings, or pH indicators, which change colour at specific pH values. Universal indicator and litmus paper are common examples.
Ion Product Constant for Water (Kw)
(Kw) is the ion product constant for water at 25°C, equal to 1.0×10−14. It represents the product of the molar concentrations of hydrogen ions ([H+]) and hydroxide ions ([OH−]) in water, indicating that the product of these ion concentrations is constant in any aqueous solution at 25°C: Kw=[H+][OH−]
