Question

Question 13
Silver articles become black on prolonged exposure to air. This is due to the formation of:
(a) ${\text{Ag}}_3\text{N}$
(b) ${\text{Ag}}_2\text{O}$
(c) ${\text{Ag}}_2\text{S}$
(d) ${\text{Ag}}_2\text{S}$ and ${\text{Ag}}_3\text{N}$

Answer 1

Option (c) is correct.

Tarnishing of silver refers to thin coating of silver sulphide bring formed on the surface of silver. Silver is not appreciably affected by dry or moist air. The presence of hydrogen sulphide in the surroundings is one of the major reasons for silver tarnish. It reacts with the silver to form silver sulphide, which is black in colour. The reaction involved is:

$2\text{Ag(s)}+{\text{H}}_2\text{S(g)}\to {\text{Ag}}_2\text{S(s)}+{\text{H}}_2\text{(g)}$