Question

Why would you reasonably expect cadmium to be a contaminant in zinc but not in silver?

Answer 1

Well, cadmium commonly forms a `Cd^(2+)` ion as does `Zn^(2+)`.

Explanation:

Silver commonly forms the univalent, `Ag^+` ion, so it could not directly replace `Zn^(2+)` in ores. As I recall, and you will have to read up on this, most heavy metal mining firms have silver, lead, zinc operations; these are a very common mixture of ores.