Question

Why do silver articles turn blackish while copper vessels turn greenish on keeping in air for a long time?

Answer 1

1. Long-term exposure to air causes silver objects to turn black. This is due to the silver sulphide (Ag₂S) layer that is created on silver objects when silver reacts with hydrogen sulphide.
2. A copper vessel reacts with carbon dioxide in humid air. A greenish layer of copper carbonate (CuCO₃) forms on the surface of copper, causing it to lose its shine.