Question

Which of the following is/are example(s) of corrosion?

• A. Rusting of iron
• B. Tarnishing of copper
• C. Liquefaction of ammonia
• D. Tarnishing of silver

Answer 1

Answer: (A), (B), (D)

The correct options are
A

Rusting of iron

B

Tarnishing of copper

D

Tarnishing of silver

Corrosion is the deterioration of the surface of a substance, mainly when exposed to factors like oxygen, moisture, carbon dioxide, chemicals, etc.

Iron ($Fe$) forms a reddish brown layer of rust, ($F{e}_2{O}_3.n{H}_{2}O$), formed when iron comes in contact with moisture and oxygen. It is called rusting of iron.

Copper ($Cu$) forms a greenish coating of basic copper carbonate, (($CuC{O}_3.Cu(OH{)}_2$), when exposed to $C{O}_2$, $O_2$ and $H_{2}O$. It is called tarnishing of copper.

Silver ($Ag$) forms a black layer of silver sulphide, ($A{g}_{2}S$), when silver is exposed to an atmosphere containing hydrogen sulphide ($H_{2}S$) gas. It is called tarnishing of silver.

Liquefaction of ammonia is not an example of corrosion but it is a process to convert gaseous ammonia to liquid ammonia.