[jennielynn_1980]

Hello again

I am really stuck on this problem:

An industrial plant that specializes in cleaning up waste liquids in confronted with the problem of seperating the metal ions found in a large vat of solution.  By analysis teh solution was found to contain varying quantities of silver, barium, and iron (III) ions.  Suggest a procedure for seperating the metal ions by precipitation.

I really don't even know where to start so if someone could nudge me in the right direction that would be much appreciated.  I am thinking it has to do with solubility but I don't know exactly what I am looking for.

[Alberto_Kravina]

I really don't even know where to start so if someone could nudge me in the right direction that would be much appreciated.  I am thinking it has to do with solubility but I don't know exactly what I am looking for.

Try to find out insoluble salts of the various metal ions.

[jennielynn_1980]

So according to the rules of solubility, if we add SO₄ ions then that would take care of both the silver and barium.  And then adding either CO₃ or PO₄ would take care of the iron (III).  If this is right, that question wasn't hard at all!  I guess I just wasn't thinking along the right lines.

[Alberto_Kravina]

So according to the rules of solubility, if we add SO4 ions then that would take care of both the silver and barium.

It will work for Barium, however, silver sulfate is moderately soluble in water. I'd suggest to use chloride ions.

And then adding either CO3 or PO4 would take care of the iron (III). 

PO₄^3- is better. I.E. iron salts are used to precipitate phosphate in water purification plants

[Borek]

Separating - does it mean you have to remove them individually, or all at the same time?

Iron will be easier to remove by raising pH - check solubility of iron hydroxide.

[jennielynn_1980]

Separating - does it mean you have to remove them individually, or all at the same time?

Iron will be easier to remove by raising pH - check solubility of iron hydroxide.

You can seperate them all together or seperately or pair two. 



Just for my own personal interest (this is not part of the homework ?), what would this look like in real life?  Would it be something like this:
you have the solution with the three metals, then you add SO₄ for the barium and it would form a salt which could be filtered out?  What would SO₄ look like? 

[Alberto_Kravina]

you have the solution with the three metals, then you add SO4 for the barium and it would form a salt which could be filtered out?  What would SO4 look like? 

You didn´t understand: SO₄ does not exist. Sulfate is a ion, it has a 2- charge => SO₄^2-
In this case, you should add a soluble sulfate, e.g. sodium sulfate or sulfuric acid.

[wereworm73]

BaSO₄ & Ag₂SO₄ are both white solids. 

Like Alberto said, I would first put a soluble chloride salt (like NaCl) to precipitate the silver ions out of solution, forming AgCl (also a white solid but can turn purplish if exposed to light long enough).