At 25 °C, what is the hydroxide ion concentration, [OH-], in an aqueous solution with a hydrogen ion concentration of [H+1=4.1 x 10-5 M?
[OH) =
M

The hydroxide ion concentration, [OH-] = 2.439 x 10⁻¹⁰

Equilibrium of water and the ions :

Kc[H₂O] is the ion equilibrium constant for water ⇒ Kw.

The product of the concentrations of these ions (H₃O⁺ and OH⁻)at equilibrium at 25°C is 1.0 x 10⁻¹⁴ M

[H₃O⁺] [OH⁻] = 1.0 x 10⁻¹⁴ M = Kw

The hydrogen ion concentration of  [H⁺]=4.1 x 10⁻⁵ M, so  the hydroxide ion concentration, [OH-] :