Ionization Constant for Water

[Ryka Vahidi 1E]

I know the ionization constant for water is 1x10^-14, but how is this number calculated?

[CristinaG]

1 x 10^-14 is the ionization constant for water and comes by solving the equilibrium constant. For the equation H20 --> H+ + OH- K = [H+][OH-] without the H2O as the denominator because it's a liquid at room temperature. Because there is one mole of H+ for every mole of OH- we can set them equal to each other. The concentration of both H+ and OH- is 1 x 10^-7 therefore K = (1 x 10^-7)(1 x 10^-7) = 1 x 10^-14

[Annie 3E]

Kw, the ionization constant for water, is found from multiplying the concentration of [H3O+] and [OH-]. Equation given as: Kw = [H3O+][OH-]. Concentration of [H3O+] in pure water at 25C is 1x10^-7. Concentration of [OH-] in pure water at 25C is 1x10^-7. So, inputting these numbers into the above equation, [H3O+][OH-] --> (1x10^-7)(1x10^-7) = Kw = 1x10^-14. This is why Kw = 1x10^-14.