The solubility product of Mg(OH)₂ is 1 10⁻¹¹ . What is the molar solubility of Mg(OH)₂ in a buffer solution of pH = 12 ?

Step-by-step solution

Given pH = 12 , the pOH of the buffer solution is 14 - 12 = 2 . The concentration of hydroxide ions is [ OH ⁻] = 10⁻² M . The dissociation of Mg(OH)₂ is given by: Mg(OH)₂(s) Mg²⁺(aq) + 2 OH⁻(aq) The solubility product expression is: K_ sp = [ Mg²⁺ ][ OH ⁻]² Let the molar solubility of Mg(OH)₂ be s . Then [ Mg²⁺ ] = s . Since it is a buffer solution, [ OH ⁻] is fixed at 10⁻² M . Substituting the values: 1 10⁻¹¹ = s (10⁻²)² 10⁻¹¹ = s 10⁻⁴ s = 10⁻⁷ M Option 1 is incorrect because it forgets to square the hydroxide ion