Question #3447f

1 Answer
Jun 11, 2015

Answer:

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