Question

What happens when OH- is added to a solution containing slightly soluble magnesium hydroxide (Mg(OH)₂, and why?

1.Solid dissolves. OH- concentration decreases. Reaction moves to the left.
2.Solid remains. OH- concentration decreases. Reaction moves to the left.
3.Solid remains. OH- concentration decreases. Reaction moves to the right.
4.Solid dissolves. OH- concentration increases. Reaction moves to the right.
5.Solid dissolves. OH- concentration decreases. Reaction moves to the right.
6.Solid remains. OH- concentration increases. Reaction moves to the right.
7.Solid remains. OH- concentration increases. Reaction moves to the left.
8.Solid dissolves. OH- concentration increases. Reaction moves to the left.

Answer 1

Adding OH- to a solution of magnesium hydroxide shifts the equilibrium to the left, leading to a decrease in the concentration of dissolved Mg2+ and an increase in undissolved Mg(OH)2.

Step-by-step explanation:

When OH− is added to a solution containing slightly soluble magnesium hydroxide, Mg(OH)2, the solution's equilibrium will be affected according to Le Châtelier's Principle.

Since OH− is a common ion in the solubility product of Mg(OH)2, adding more OH− will shift the equilibrium to the left, as the system attempts to counter the increase in OH− concentration.

This will result in a decrease of soluble Mg2+ concentration and an increase in the amount of undissolved Mg(OH)2. Therefore, the solid Mg(OH)2 remains, the OH− concentration increases due to its addition but the reaction's shift to the left leads to less Mg(OH)2 being dissolved.