Water ionization is the process by which water molecules dissociate or break apart into ions in an aqueous solution. In water, a small fraction of water molecules naturally undergo ionization to form hydronium ions (H₃O⁺) and hydroxide ions (OH⁻).
The ionization of water is represented by the following chemical equation:
H₂O ⇌ H⁺ + OH⁻
The equilibrium constant of ( Kc ) of water is given by,
\( K_c = \frac{[H^+][OH^-]}{[H_2O]}\)
The square brackets represents the molar concentration of species and its units are mole dm. As we know that ionization of water is very small so the concentration is approximately unchanged and consider as constant (KW) so, the equation will be :
KC[H2O] = [H+][OH–]
KC[H2O] = KW
KW = [H+][OH–]
Where Kw is ionic product constant of water and its value is ;1 (mol/dm3)2 at room temperature 25°C.
pH is a measure of the acidity or alkalinity (basicity) of a solution. It quantifies the concentration of hydrogen ions (H⁺) present in a solution.
Mathematically, pH is defined as:
pH = -log[H⁺]
Where [H⁺] represents the concentration of hydrogen ions in moles per liter (mol/L).
pOH is a measure of the hydroxide ion (OH⁻) concentration in a solution. It is the negative logarithm of the hydroxide ion concentration.
Mathematically, pOH is defined as:
pOH = -log[OH⁻]
Where [OH⁻] represents the concentration of hydroxide ions in moles per liter (mol/L).
The Danish biochemist S. P. L. Sørensen devised the pH scale while working on the brewing of beer. The pH scale is a numerical scale used to specify the acidity or basicity (alkalinity) of a solution. It quantifies the concentration of hydrogen ions (H⁺) in a solution and ranges from 0 to 14.
