# Why is only the carbonate anion used to precipitate Barium?

Q: Why is the $$\ce{CO3^2-}$$ anion used to precipitate Barium from $$\ce{BaBr2}$$ and not another anion, such as $$\ce{PO4^3-}$$, or $$\ce{SO4^2-}$$?

I am studying high school Chemistry, and the current unit is precipitations. The worked example states that $$\ce{Na2CO3}$$ can be used to precipitate $$\ce{Ba^2+}$$ from a solution of $$\ce{BaBr2}$$, which makes sense.

However, it does not explain why the $$\ce{CO3^2-}$$ anion should be selected, when according to the solubility table $$\ce{SO4^2-}$$ and $$\ce{PO4^3-}$$, would both be able to precipitate $$\ce{Ba^2+}$$ from $$\ce{BaBr2}$$. Am I missing something obvious? Why is it that the $$\ce{CO3^2-}$$ anion is favoured over the other two anions? `

• Do you have solubility product constants? That may tell you something. – Oscar Lanzi Sep 1 '19 at 0:25
• Who said that they’re not? Sulfate is commonly used to precipitate barium. Barium sulfate is an extremely insoluble compound. – Gimelist Sep 1 '19 at 0:27
• I don't have solubility product constants, but it seems that the choice of CO3 was just an oversimplification on the part of the publisher. Thank you both for your help! – Archie Sep 1 '19 at 0:36