As far as I can tell the answer for all of them is dissolution but wanted to ask anyway just in case I was wrong and get a proper answer along with explanation.

With reference to Table 4.2, suggest one method by which you might separate (a) K+ from Ag+, (b) Ba2+ from Pb2+, (c) NH4+ from Ca2+, and (d) Ba2+ from Cu2+. All cations are assumed to be in aqueous solution, and the common anion is the nitrate ion.

Question

As far as I can tell the answer for all of them is dissolution but wanted to ask anyway just in case I was wrong and get a proper answer along with explanation.

With reference to Table 4.2, suggest one method by which you might separate (a) K+ from Ag+, (b) Ba2+ from Pb2+, (c) NH4+ from Ca2+, and (d) Ba2+ from Cu2+. All cations are assumed to be in aqueous solution, and the common anion is the nitrate ion.

anonymous · Answer

I know I am supposed to combine the elements into a compound but what for they are positive charged ions and the one is soluble and the other is insoluble.  I asked my teacher about it but he is not supper helpful and just says go to the book which isn't understandable.