A solution containing a mixture of metal cations was treated with dilute HCI and no precipitate formed. Next, HS was bubbled through the acidic solution. A precipitate formed and was filtered off. Then, the pH was raised to about 8 and HS 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. Classify the metal ions based on whether they were definitely present, definitely absent, or whether it is possible they were present in the original mixture.

Mn2+
Sn4+
Hg2+
Ag+
Ca2+
Cr3+
Hg2 2+
Cu2+
Fe2+
Li+
Mg2+
Sb3+
Pb2+​