Question

A student has found black coating on his silver coins
and green coating on his copper coins. Which chemical
phenomenon is responsible for this ? Write chemical
name of these coatings.
[2 Marks]​

Answer 1

Explanation:

The chemical phenomenon which is responsible is corrosion.

When a metal is attacked by substances around it such as moisture, acids, etc. it is said to corrode and this process is called corrosion.

After corrosion, the color of:

Silver changes to → black

Copper changes to → green

the chemical name of black coating is silver sulphide and green coating is copper carbonate.