Question

a numistmatist (coin collect) has been collecting god coin, silver coins and copper coin for a long time. one day he observed a black coating on silver coin and green coating on copper coins. what chemical process is responsible for these cotings. also name chemical formula of the black and green coating

Answer 1

a)corrosion:- tarnishing of silver and copper in this case.
b)black- silver sulphide
green- copper oxide