Question

The maximum pH of a solution which is 0.10 M in Mg²⁺ from which Mg(OH)₂ is not precipitated is [Given : K_sp of Mg(OH)₂ = 1.2 x 10^-11 M³]

(A) 4.96 

(B) 6.96 

(C) 7.54 

(D) 9.04

Answer 1

Correct option (D) 9.04

Explanation : 

The concentration of OH^- which is required to prevent the precipitation of Mg(OH)₂ is

This is the maximum concentration of OH^- which could prevent the precipitation of Mg(OH)₂ , as it can be seen that any concentration of OH^- ions less than this would still have the I.P < K_sp, hence in such cases also the precipitation would not occur. So , pOH would be minimum and pH would thus be maximum.