Question

Silver jewellery becomes black on prolonged exposure to air, it is due to the formation of

Answer 1

silver sulphide( black) is formed.
silver reacts with sulphur present in air and firms a black colour layer on the metal surface

Answer 2

Silver objects turn black due to the formation of a layer of silver sulfide (Ag2S) on their surface. Traces of hydrogen sulfide (H2S) present in air react with silver to form silver sulfide, which gives the metal black apperance