I'm taking Chem II over the summer at a junior college and was given this problem on one of my homework assignments: I am told I have a sol'n containing the cations Ag, Al, As, Ba, Bi, Ca, Cd, Co, Cr, Cu, and Fe. My objective is to write all the compounds that would be precipitated if hydrochloric acid is added to the above sol'n. My instincts are telling me to just use the solubility rules. For example, when Ag and hydrochloric acid combine, AgCl is formed but according to the solubility rules AgCl is insoluble so AgCl would be one of the compounds that would be precipitated. Am I going about this all wrong or what? The 2nd part says that a reagent is now needed tha will precipitate the smalest number of remaining cations and that the best reagent for this is hydrogen sulfide plus hydrochloric acid. It then asks me to find all the compounds that would be precipitated. Do I just go about this the same way for the first part? I don't understand when they say 'smallest number of cations'. Please can anyone help me with this?