Question

When a vessel is exposed to moist air for a long time,then a green coating is formed on its surface.The vessel must be made of :

(a) zinc

(b) magnesium

(c) iron

(d) copper

Answer 1

Copper metal when exposed to air turns green in colour due to corrosion. When copper vessel is exposed to air in rainy season, the metal reacts with gases and moisture and atmospheric gases to form a mixture of copper carbonate and copper hydroxide. This gives a green colour to the surface of copper metal.

The reaction is as follows:

2Cu + H₂O + CO₂ + O₂ → Cu(OH)₂ + CuCO_{3
so option d is correct}