2020 · Q23
Silver articles become black after some time when exposed to air because
General KnowledgeChemistry
- ASilver gets oxidized to silver oxide.
- BSilver reacts with moist carbon dioxide in the air to form silver carbonate.
- CSilver reacts with sulphur in the air to form a coating of silver sulphide.
- DSilver reacts with nitrogen oxides in the air to form silver nitrate.
Explanation
Air contains traces of sulphur compounds such as hydrogen sulphide. Silver reacts with sulphur to form a black coating of silver sulphide (Ag2S), which is the tarnish seen on old silver articles. The blackening is not oxidation to silver oxide, nor the formation of silver carbonate or silver nitrate. Hence C.