A neutral solution means we are having equal amount of H⁺ and OH⁻. As we know,
Kw = [H⁺] [OH⁻] ------ (1)
So, in order to calculate Kw we first need to calculate [H⁺] and [OH⁻],
As, pH = -log [H⁺]
Or,
[H⁺] = 10⁻ˣ ∴ x = pH = 7.61
Putting value, and solving
[H⁺] = 2.45 × 10⁻⁸
As, our system is neutral, so concentration of [OH⁻] is exactly equal to concentration of [H⁺]. Now, putting values of [H⁺] and [OH⁻] in equation 1.
Kw = [2.45 × 10⁻⁸] [2.45 × 10⁻⁸]
Kw = 6.00 × 10⁻¹⁶
