Question

Determine the molar solubility of Fe(OH)₂ in pure water. K_sp for Fe(OH)₂)= 4.87 × 10^-17.

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Answer 1

Fe(OH)2 (s) <=> Fe2+ + 2 OH-

let x = mol/L of Fe(OH)2 that dissolve : this will give x mol/L Fe2+ and 2 mol/L OH-

Ksp = 4.87 x 10^-17 = [Fe2+][OH-]^2 = (x)(2x)^2 = 4 x^3

x = molar solubility =2.30 x 10^-6 M

Answer 2

Fe(OH)2 (s) <-> Fe2+ + 2 OH- let x = mol/L of Fe(OH)2 that dissolve : this will give x mol/L Fe2+ and 2 molL OH- Ksp 4.87 x 10^-17s Fe2+][OH-)^2 = (x)(2x)^2+ 4 x^3 x - molar solubility -2.30 x 10-6 M