Question

After the reaction in part B of the experiment has reached equilibrium, namely

Mg(OH)2 (s) <--> Mg2+ (aq) = 2OH- (aq)
the equilibrium will shift to the left if MgCl2 (aq) is added

a. true
b. false

Answer 1

The addition of magnesium chloride, which provides a common ion (Mg2+), to a solution at equilibrium with magnesium hydroxide, will cause the equilibrium to shift to the left, resulting in an increase in the formation of solid Mg(OH)2.

Step-by-step explanation:

The student's question revolves around the solubility equilibrium of magnesium hydroxide and the effect of adding a common ion on this equilibrium. The reaction in question is Mg(OH)2 (s) ↔ Mg2+ (aq) + 2OH- (aq), which is in dynamic equilibrium when dissolved in water.

Adding magnesium chloride (MgCl2), a source of Mg2+ ions, to the solution already containing ions from dissolved magnesium hydroxide will indeed cause a shift in the equilibrium. According to Le Châtelier's principle, this addition will increase the concentration of Mg2+ ions in the solution, leading to a shift of the equilibrium to the left.

This shift will decrease the concentration of hydroxide ions (OH-) and result in the formation of more solid Mg(OH)2, thus making the initial statement true.