Like all equilibrium constants, Kw varies somewhat with temperature. Given that Kw is 3.31 * 10-13 at some temperature, compute the pH of a neutral aqueous solution at that temperature.

Since Kw = [H⁺][OH⁻], and the concentration of both substances are the same, the equation is now Kw=[H⁺]²

So,

3.31x10⁻¹³ = [H⁺]²

Take the square root = 5.75x10⁻⁷

Then take the negative log to find the pH:

-log (5.75x10⁻⁷) = 6.25