Question

Predict the effect on the molar solubility of Mg(OH)2

(higher, lower, no change) with an explanation:

a.) Mg(OH)2 was dissolved in a solution of 0.1 M HCl

HCl --> H3O+ + Cl-

Mg(OH)2 --> Mg2+ + 2OH-

Answer 1

Mg(OH)2 is a sparingly soluble salt. When it dissolves in water it dissociates as

Mg(OH)2 ---------> Mg2+ + 2OH-

so when we dissolve Mg(OH)2 in 0.1 M HCl the H3O+ from the acid reacts with the OH- present in solution.So when the OH- will be removed from the solution more Mg(OH)2 will become soluble.

So when dissolved in 0.1 M HCl molar solubility of Mg(OH)2 is higher.