Question

Why silver turns into black after a long time? Give the reason.

Answer 1

Silver:

• Silver has the chemical symbol$\mathrm{Ag}$ and the atomic number$47$.
• Silver, a transition metal, is a solid at ambient temperature.

Tarnishing of silver:

• When silver is exposed to sulfur-containing gases in the air, it decolorises and subsequently darkens as it combines with the gas to develop a layer of tarnish on the surface.
• This is known as tarnishing.
• Tarnishing is caused by a chemical interaction between silver and sulfur-containing compounds in the air.
• Silver sulphide is formed when silver is tarnished
• Silver sulphide is a dark substance.
• A thin layer of silver sulphide grows on the surface of silver, darkening it.
• $$\begin{gathered} 4\mathrm{Ag}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{S}\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{Ag}}_2\mathrm{S}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Black}\mathrm{coating} \end{gathered}$$