Question

Question #3447f

Answer 1

This reaction produces hydroxyapatite and hydroxide anions.

Explanation:

When calcium hydroxide, `Ca(OH)_2`, reacts with phosphate ions, `PO_3^(3-)`, the reaction produces hydroxyapatite, `Ca_5(PO_4)_3OH`, which precipitates out of the solution, and hydroxide anions, `OH^(-)`.

The balanced chemica lequation for this reaction looks like this

`5Ca(OH)_(2(aq)) + 3PO_text(4(aq])^(3-) -> Ca_5(PO_4)_3OH_text((s]) darr + 9OH_((aq))^(-)`

The complete ionic equation looks like this

`5Ca_((aq))^(2+) + 10OH_((aq))^(-) + 3PO_(4(aq))^(3-) -> Ca_5(PO_4)_3OH_text((s]) + 9OH_((aq))^(-)`

If you remove spectator ions, which are ions present on both sides of the equation, you get the net ionic equation

`5Ca_((aq))^(2+) + OH_((aq))^(-) + 3PO_(4(aq))^(3-) -> Ca_5(PO_4)_3OH_text((s])`

This reaction is actually used to remove phosphate ions from various solutions.

Here's how the structure of hydroxyapatite looks like:

![http://www.chemtube3d.com/solidstate/SShydroxyapatite.htm]()