If [H⁺] = 1.0x10^-4 moles per liter let's calculate the hydroxide ion concentration, [OH^-].

First Step:

Substitute the hydrogen ion concentration in the equation:

[H⁺][OH^-] = 10^-14

[1.0x10^-4][OH^-] = 10^-14

Second Step:

Solve for [OH^-]:

[OH^-] = 1.0x10^-14 / 1.0x10^-4

[OH^-] = 1.0x10^-10 moles / liter