Question

Metals like iron, aluminium, cobalt and nickel become passive when treated with pure concentrated nitric acid.

• A. True
• B. False

Answer 1

The correct option is A

True

Metals like iron, aluminium, cobalt and nickel become passive when treated with pure concentrated nitric acid. It is due to the formation of an extremely thin layer of insoluble metallic oxide (passivity) which stops the reaction. Passivity can be removed by rubbing the surface layer with sand paper or by treating with strong reducing agents.