Ionic Product of Water
Ionic Product of Water
Ionic Product of Water (Kw) is the equilibrium constant for the reaction in which water undergoes an acid-base reaction with itself. That means water is behaving simultaneously as both an acid and a base.H2O ⇌ H+ + OH−
Equilibrium Constant-
K = [H+] [OH−]/[H2O]
or, K . [H2O] = [H+] [OH−]
or, Kw = [H+] [OH−] (as the concentration of H2O is constant)
The constant Kw, is called the dissociation constant or ionic product constant of water.
For pure water-
[H+] = [OH−] = 10−7M at 25oC
so, pH = pOH = 7 at 25oC
and Kw = 10−7 X 10−7 = 10−14
and, pKw = 14
Number of water moles in 1 liter of water = 1000/18 = 55.5 moles
number of water molecules in 1 liter water = 55.5 NA
Concentration of H+ or OH− ions = 10−7mol/liter
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