Question

Why do silver articles turn black when kept open for a few days?
(a) Name the phenomenon involved.
(b) Name the black substance formed and give its chemical formula.

Answer 1

• Silver article turns black when kept in the air because silver article reacts with sulphur compounds such as hydrogen sulphide $\left(H_{2}S\right)$ present in air.
  

$Ag+H_{2}S\to A{g}_{2}S+H_2$

• The phenomenon is called corrosion. For silver particularly, it is called tarnishing of silver.
  
• Silver sulphide $\left(A{g}_{2}S\right)$ is the black substance formed