A solution contains some or all of the ions Cu^2+, Al^3+, K^+, Ca^2+, Ba^2+, Pb^2+, and NH4^+. The following tests were performed, in order, on the solution.
1. Addition of 6 M HCl produced no reaction.
2. Addition of H2S with 0.2 M HCl produced a black solid.
3. Addition of (NH4)2S produced a white solid.
4. Addition of (NH4)2HPO4 in NH3 produced no reaction.
5. The final supernatant when heated produced a purple flame.
Identify which of these ions were present in the solution, which were absent, and which ones no conclusions can be drawn.
Drag the appropriate items to their respective bins.