Asolution contains some or all of the ions cu2+, al3+, k+, ca2+, ba2+, pb2+, and nh4+. the following tests were performed, in order, on the solution. addition of 6 m hcl produced no reaction. addition of h2s with 0.2 m hcl produced a black solid. addition of (nh4)2s produced a white solid. addition of (nh4)2hpo4 in nh3 produced no reaction. the final supernatant when heated produced a purple flame. identify which of these ions were present in the solution, which were absent, and for which ones no conclusions can be drawn.