Question

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

Answer 1

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.