An aqueous solution at 25∘C has a hydronium ion concentration of 3.2*10-9 M. What is the hydroxide ion concentration of the solution? Write your answer in scientific notation. Use the multiplication symbol rather than the letter x in your answer. Report your answer two significant figures.

3.1 * 10⁻⁶ M

Explanation:

One water molecule can react as a base while other water molecule acts as an acid to form and hydronium ion and a hydroxide ion.

H₂O (l) + H₂O (l) ⇄ H₃O⁺ (aq) + OH⁻ (aq)

The equilibrium constant (Kw), known as the ionic product of water, has the following form:

Kw = [H₃O⁺] * [OH⁻]

The value of Kw at 25°C is 1.0 * 10⁻¹⁴.

An aqueous solution at 25°C has a hydronium ion concentration of 3.2 * 10⁻⁹ M. The hydroxide concentration is:

Kw = [H₃O⁺] * [OH⁻]

1.0 * 10⁻¹⁴ = 3.2 * 10⁻⁹ * [OH⁻]

[OH⁻] = 3.1 * 10⁻⁶ M