Question

2. Determine if each compound is more soluble in acidic solution or in pure water. Explain.

a. Hg2Br2

b. Mg(OH)2

Answer 1

2. An acid solution contains H⁺ ions.

(a) Hg₂Br₂ is an ionic compound. Thus it gets completely dissociated into water forming Hg₂²⁺ and Br^– ion. Also in acid solution when this Br^– ion react with H⁺ ion they form HBr which is also a strong acid. Thus HBr also gets completely ionized in solution. Thus solubility of Hg₂Br₂ does not get effected by dissolving it in acid solution.

Therefore Hg₂Br₂ is more soluble in pure water.

(b) The compounds containing OH^– ions react with H⁺ in acid solutions and form water.

H⁺ + OH^– = H₂O

Thus as more and more OH^– ions come to solution the above reaction proceeds in forward direction and the compound gets more and more ionized into the acid solution.

Mg(OH)₂ dissociates into Mg²⁺ and OH^– as follows:

Mg(OH)₂ = Mg²⁺ + 2 OH^–

Thus this OH^– react with H⁺ in acid solution and makes Mg(OH)₂ more soluble in acid solution.

Therefore Mg(OH)₂ is more soluble in acidic solution.