At the freezing point of water (0oC), Kw = 1.2x10-15, Calculate [H+] and [OH-] for a neutral solution at this temperature.

Answer 1

Kw is the auto-ionization constant for water (H2O). It will vary with temperature.

H₂O <==> H⁺ + OH^- .. auto-ionization of water

Kw = [H⁺][OH^-]

1.2x10^-15 = [H⁺][OH^-] = (x)(x)

1.2x10^-15 = x²

x = 3.46x10^-8 M = [H⁺] = [OH^-]