Determine the molar solubility of fe(oh)2 in pure water. ksp for fe(oh)2= 4.87 × 10-17

Answer is: molar solubility of iron(II) hydroxide is 2,3·10⁻⁶ M.
Chemical reaction: Fe(OH)₂(s) → Fe²⁺(aq) + 2OH⁻(aq).
s(Fe(OH)₂) = ?M.
s(Fe(OH)₂) = s(Fe²⁺) = x.
s(OH⁻) = 2s(Fe(OH)₂) = 2x.
Ksp = s(Fe²⁺) · (s(OH⁻))².
Ksp = x · (2x)².

4,87·10⁻¹⁷ = 4x³.

x = ∛(4,87·10⁻¹⁷ ÷ 4).

x = 2,3·10⁻⁶ M.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.