Question

Question #83607

Answer 1

There are several possibilities for X. I'll nominate copper(II) chloride.

Explanation:

Copper(II) chloride is `CuCl_(2(aq))`. It is readily soluble. No precipitate would occur if chloride, sulfate or nitrate ions were added because these ions are all soluble with copper(II).

Copper(II) carbonate is a green, insoluble substance so a green precipitate would result if carbonate ions were added:

`Cu_((aq))^(2+)+CO_(3(aq))^(2-)rarrCuCO_(3(s))`

Answer 2

Another candidate is magnesium nitrate.

Explanation:

The idea here is that you're looking for a cation that will not form a precipitate when mixed with those three anions, chloride, sulfate, and nitrate, but that it will form one when mixed with a solution that contains carbonate anions.

My cation of choice is the magnesium cation, `"Mg"^(2+)`. When mixed with carbonate anions it forms magnesium carbonate, a white insoluble solid that precipitates out of solution.

`"Mg"_text((aq])^(2+) + "CO"_text(3(aq])^(2-) -> "MgCO"_text(3(s]) darr`

Magnesium chloride, `"MgCl"""_2`, magnesium sulfate, `"MgSO"_4`, and magnesium nitrate, `"Mg"("NO"_3)_2`, are all soluble compounds, so they will not precipitate out of solution when solution `X` is mixed with the chloride, sulfate, and nitrate solutions.

If you assume that solution `X` can contain one of the anions with which it does not form a precipitate when mixed, then you can say that solution `X` can be magnesium nitrate, magnesium sulfate, or magnesium chloride.