Ionization of Water:
Water molecules exist in equilibrium with hydrogen ions and
H2O <--> H+ + OH-
The water equilibrium constant is written as:
Kw = [H+] [OH-]
Experimentally, it has been found that the concentration of:
H+ = OH- = 10-7
Therefore: Kw = [10-7][ 10-7] = [10-14]
(To multiply exponential numbers - simply add the exponents.)
The values for Kw, H+, OH- concentration
all indicate that the equilibrium favors the reactant (water
molecules). In other words, only very small amounts of H+
and OH- ions are present.
Effect of Acids and Bases on Water Equilibrium:
If an acid (H+) is added to the water, the equilibrium
shifts to the left and the OH- ion concentration decreases.
Water Equilibrium: H2O <--> H+
If base ( OH-) is added to water, the equilibrium
shifts to left and the H+ concentration decreases.
Water Equilibrium Principle: The multiplication product
(addition of exponents) of H+ and OH- ion
concentration must always be equal to 10-14.
BOTH H+ and OH- ions are ALWAYS PRESENT
in any solution. A solution is acidic if the H+ are
in excess. A solution is basic, if the OH- ions are