Question

The red or orange coating that forms on the surface of iron when exposed to air and moisture for some time is called:
A. galvanization
B. electroplating
C . rust
D. reduction

Answer 1

Hint: When iron is exposed to the air and moisture, iron metal reacts with the water and gets oxidized to hydrated iron oxide. This iron oxide looks like flakes and cannot protect the iron surface. the oxidation of the iron in the surface flakes off.

Complete step by step answer:
Iron oxide is generally reddish brown in colour. It is formed by the reaction of iron water and oxygen. The red or orange colour is also observed as the colour of the iron oxide.
Therefore, the red or orange coating that forms on the surface of iron when exposed to air and moisture for some time is called rust. And the overall process of formation of rust is rusting of iron.
In the rusting of iron, the increase of oxidation state of iron is caused by loss of electrons. The formula of the rust or iron oxide is \[F{e_2}{O_3}.x{H_2}O\].

So, the correct option is (C).

Note:
Remember that rust or iron oxide formula is \[F{e_2}{O_3}.x{H_2}O\]. Generally, the colour of Iron oxide is reddish brown. Rust is formed by the reaction between iron, water and oxygen. Red or orange coloured iron oxide is also observed. This overall process of formation of rust is rusting of iron.