Science Buddies: "Ask an Expert"

Hi,

From my previous research I have found that calcium carbonate chemically bonds with phosphate and reduces the phosphates. What is the chemical equation for this? CaCO2 + PO3 --> ?

Thanks
Andrew

Hi Andrew,

If you've been googling "calcium carbonate phosphate reaction" or "CaCO2 + PO3" (which were my first moves), the problem you're having is the definition of phosphate. Check this out:

http://en.wikipedia.org/wiki/Phosphate

Basically, "phosphate" isn't a specific compound, it's a class of compounds in which a P atom is at the center with four oxygens surrounding it. Up to three of these oxygens can each be attached to an additional atom or functional group, so you can have calcium monophosphate, calcium triphosphate, etc. There is also a phosphate ion, PO₄^3-. And some other varieties -- see the Wikipedia entry or search elsewhere.

Does your source say what kind of phosphate is involved? If not, what's the context -- a biological system, soil, water pollution, other? That might help you or us figure it out.

Another possible issue: When you say "reduces the phosphates", do you mean reduces the amount of phosphate present by changing it into something else, or reduce in the chemical reaction sense? [ http://en.wikipedia.org/wiki/Reduction_(chemistry) ]

Hope that helps, and please do ask more questions if you still can't figure it out!

Amanda

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PO₄^3-

is PO4 with a net charge of 3-.