What is the [OH^-] of [H3O^+]= 2.0 • 10^-9 M

Answer 1

At 25 ^oC the ion product for water is K_w = [H₃O⁺][OH^-]=1x10^-14 mole²/Litre²

Thus, if the hydronium ion concentration [H₃O⁺] = 2.0 x 10^-9M.

The [OH^-] = (1 x 10^-14) / (2.0 x 10^-9)

i.e. [OH^-] = 0.5 x 10^-5 M = 5 x 10^-6 M

NB: mole/Litre = Molarity(M)