posted by Brunost .
A solution containing a mixture of metal cations was treated with dilute HCl and no precipitate formed. Next, H2S was bubbled through the acidic solution. A precipitate formed and was filtered off. Then, the pH was raised to about 8 and H2S was again bubbled through the solution. A precipitate again formed and was filtered off. Finally, the solution was treated with a sodium carbonate solution, which resulted in no precipitation. Which metal ions were definately present, which were definitely absent, and which may or may not have been present in the original mixture?
Ag+, Ba2+, Mg2+, Hg2+, Pb2+, Hg2^2+, Cu2+, Zn2+, Ni2+, Co2+, Sn2+, Li+, Sb3+
I understand how to find out which ones POSSIBLY are there, but how can one find out which ones are DEFINITELY there?
Well, its definitely too late to help you, but I'll post this for the benefit of others. None of the listed atoms are definitely present, as there is no way to tell from the limited information. Likewise, we know from the chart of the seperation of cations that Ba2+ and Ca2+ have no chance of being there, since they form precipitates when carbonate is added. Ag+, Pb2+, and Hg2^2+ have no chance of being there either, since they form precipitates when dilute HCl is first added. The rest on the list are all possibly there.