Given : Ksp = 1.4 × 10-11 ; S = ?
Magnesium hydroxide dissociates as shown below :
Mg(OH)2 ⇌ Mg2+ + 2(OH)-
Ksp = [Mg2+] [OH-]2
Let the solubility of Mg(OH)2 be S mol dm-3.
∴ [Mg2+] = Concentration of Mg2+ions
= S mol dm-3
∴ [OH-] = Concentration of OH- ions
= 2S mol dm-3
∴ Ksp = S × (25)2 = 4S3
Ksp = 1.4 × 10-11
∴ 1.4 × 10-11 = 4S3
S = 1.518 × 10-4 mol dm-3
∴ Solubility of Mg(OH)2 = 1.518 × 10-4 mol dm-3
