What is the [H3O+] in a solution with [OH-]=1x10^-12 M

Question

I know the answer is kw=[H3O][OH] = 1 x 10^-14 / 1 x 10^-12 and 0.01 M but i dont understand HOW they got that answer

Answer 1

The way to get the answer is to know and understand certain relationships between [H₃O⁺] and [OH-]. One such relationship which you must know (memorize) is...

[H₃O⁺] [OH-] = 1x10^-14 = Kw (the rest is algebra)

[H₃O⁺] [1x10^-12] = 1x10^-14

[H₃O⁺] = 1x10^-14 / 1x10^-12

[H₃O⁺] = 1x10^-2 = 0.01 M