What is the balanced chemical equation that describes the dissociation of the strong base magnesium hydroxide, Mg(OH)2 in water?

1 Answer
Ernest Z.
Jul 14, 2014

The equation is #"Mg(OH)"_2"(s)" ⇌ "Mg"^"2+""(aq)" + "2OH"^"-""(aq)"#.

Explanation:

# "Mg(OH)"_2# is a strong base.

#"Mg"# is a Group 2 Metal, so it form #"Mg"^"2+"# ions. Each ion pairs up with two #"OH"^"-"# ions to form the neutral compound, # "Mg(OH)"_2#.

Magnesium hydroxide is "insoluble", so only a small amount it goes into solution. But every bit that goes into solution dissociates into #"Mg"^"2+"# ions and #"OH"^"-"# ions.

There is a dynamic equilibrium between the solid compound and the ions in solution.

#"Mg(OH)"_2"(s)" ⇌ "Mg"^"2+""(aq)" + "2OH"^"-""(aq)"#

The #"Mg"^"2+"# ions and the #"OH"^"-"# ions are leaving the surface of the solid at the same rate as they return from the solution to the surface of the solid.

Here's a video showing the process.

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