Answer:
[OH⁻] = 1.21×10⁻⁷
Step-by-step explanation:
Water dissociates in the solution as:
H₂O ⇔ H⁺ + OH⁻
For pure water, the concentration of [H⁺] and [OH⁻] are equal.
Kw is defined as the product of the active concentration of H⁺ and OH⁻ furnished by the water.
So,
Kw = [H⁺] [OH⁻]
Given that, at 30.0 °C, the Kw is 1.47×10⁻¹⁴
So,
Kw = [H⁺] [OH⁻]
As stated above, [H⁺] = [OH⁻]
1.47×10⁻¹⁴ = [OH⁻]²
[OH⁻] = 1.21×10⁻⁷