Water Equilibrium Constant and Acid Base Strength

Water Equilibrium Constant
Water is a very weak electrolyte. Ionization occurs in water:
H₂O → H⁺ + OH^-

K _[H2O] = [H⁺] [OH^-]
Kw = [H⁺] [OH^-]
At a temperature of 25ºC, Kw = 1.10^-14, so that [H⁺] = [OH^-] = 1.10^-7.
Acid solution [H⁺]> 1.10^-7.
Base solution [OH-] < 1.10^-7.

Acid Base Strength
Acid base strength expressed in H⁺ or OH^- concentration. Acid with the high concentration of H⁺ has greater acid strength than with the acid H⁺ with low concentration. Similarly base with its concentration of OH^-.
Example:
HCl → ....H⁺ ....+ ...Cl^-
0.1 M .. 0.1 M 0....0.1 M
H₂SO₄ → ....2H⁺ ...+ ..SO₄^2-
0.1 M .....0.2 M...... 0.1 M
At the same concentration (0.1 M), H₂SO₄ is more acid than HCl because the H₂SO₄ has greater H⁺ concentration than HCl.