Question

You are presented with an unknown that possibly has Ag+, Bi3+, Sn4+, Zn2+, Co2+ and Na+. You divide the solution into three equal volumes, labeling one “A,” one “B,” and one “C.” To “A” you add 6 M HCl and do not observe any precipitate forming. In tube B, you add 6 M HCl until the pH is 0.5 then add thioacetamide and heat the solution in a hot water bath for seven minutes, eventually observing a black precipitate. You take solution “C,” pour it into a 50 mL beaker and evaporate it to dryness on a hot plate. This leaves behind a small amount of white crystals scattered on the walls and bottom of the beaker. Identify what ions COULD be confirmed as present in the unknown based on the observations from each tube and the set of possible ions. Give a brief justification of your answers.