For precipitation of silver from the complex `[Ag(CN)_(2) ]^(-)` , zinc is used but not copper. Why?

Explanation

Copper is also more electropositive than silver. Thus practically copper can also precipitate silver from `[Ag(CN)_2]^(-)`. But zinc is more electropositive when compared with copper and zinc is cheaper than copper.
Thus zinc is used commonly to precipitate silver from `[Ag(CN)_2]^(-)`