An unknown soln (blue color) contains one cation from group 1:Ca 2+ , Ba 2+ or S

Question

An unknown soln (blue color) contains one cation from group 1:Ca2+, Ba2+ or Sn2+, anothercation from group 2 :Cu2+ or Ni2+, onemore cation from group 3: Mg2+ or Zn2+ I am trying to separate the group 1 from group 2 and group 3,then find out what one cation from group 1. I added some (NH4)2CO3 to thesoln, I expected some ppt, but there are onlyvery tiny white ppt, which I have to look closely. I almostmissed it. I have tried (NH4)2SO4 too. Iexpected to get some ppt. The soln turn the color from blue tocolorless, also it was hardly found any ppt. Since Cu, Ni, Mg and Zn will dissolve inCO32- / SO42- , andCa2+ has the highest solubility in group 1: Ca2+, Ba2+and Sn2+. Would the result suggest that Ca2+ has the biggestchance to be the cation in the unknown soln? What should I do to confirm it afterward because there arejust too little ppt. Centrifuge the soln doesn't even help toseparate them. Thank you. An unknown soln (blue color) contains one cation from group 1:Ca2+, Ba2+ or Sn2+, anothercation from group 2 :Cu2+ or Ni2+, onemore cation from group 3: Mg2+ or Zn2+ I am trying to separate the group 1 from group 2 and group 3,then find out what one cation from group 1. I added some (NH4)2CO3 to thesoln, I expected some ppt, but there are onlyvery tiny white ppt, which I have to look closely. I almostmissed it. I have tried (NH4)2SO4 too. Iexpected to get some ppt. The soln turn the color from blue tocolorless, also it was hardly found any ppt. Since Cu, Ni, Mg and Zn will dissolve inCO32- / SO42- , andCa2+ has the highest solubility in group 1: Ca2+, Ba2+and Sn2+. Would the result suggest that Ca2+ has the biggestchance to be the cation in the unknown soln? What should I do to confirm it afterward because there arejust too little ppt. Centrifuge the soln doesn't even help toseparate them. Thank you.

Explanation / Answer

This is a hard question to answer because I don't know howmuch/what the pptes looked like. More importantly, I don't knowwhat lab this is (what course etc) and super importantly, I don'tknow what you're idea of a lot or a little amount of ppte is! That being said, the only thing that comes to mind to test forCa++ in solution is a complexometric titration with EDTA. But thatalso picks up Mg++. That probably doesn't help, but I also knowthat there are simple water test kits that you can get that do avery similar titration rxn.. you drop in blue drops and it turnspurple at the end point etc. Your best bet would be to ask someone who knows more aboutwhat you're doing than anyone here.. or search google for atest for Ca++ based on what you need.. think about whether ornot you need to recup the ions or not, etc. Based on your results above though, you said that Ca++ has thehighest solubility in group 1, but it remained in solution, whichis no surprise when you added carbonate and sulfate. But so did theother ions... it is hard to conclude you have Ca++ based on that.Remember that a ppte may re-dissolve readily if you haven't addedenough agent to ppte it out of solution, or other factors may bepresent too, for example, if the solution is warm, it may morequickly redissolve. I can't come up with anything else, sorry I couldn't be morehelp!

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