Question

In moist air, iron is oxidized to give:
A.Iron (II) oxide
B.Iron (III) oxide
C.Iron (II) hydroxide
D.Iron (II) sulfide

Answer 1

Hint: We have to know that the process of formation of metal oxide on contact to moist air is called corrosion. Corrosion takes place in the presence of moisture.

Complete step by step answer:
We have to know that when Iron metal reacts with moist air by oxidation, it forms a hydrated iron oxide. This does not guard the iron surface to further reaction as it flakes off, exposing more iron metal to oxidation. This process is known as rusting. Iron powder is pyrophoric in nature, making it a risk to fire.
When we heat iron in the presence of oxygen, we get the products as iron (III) oxide and iron (II,III) oxide. We can write the reaction as,
$4Fe\left( s \right) + 3{O_2}\left( g \right) \to 2F{e_2}{O_3}\left( s \right)$
$3Fe\left( s \right) + 2{O_2}\left( g \right) \to F{e_3}{O_4}\left( s \right)$
The following oxidation reaction takes place, when iron reacts to moist air:
$Fe \to F{e^{2 + }} + 2{e^ - }$
Iron gets oxidized to Iron (II).
The following reaction occurs in the presence of moisture.
$2F{e^{2 + }} + 2{H_2}O + \dfrac{1}{2}{O_2}\xrightarrow{{}}F{e_2}{O_3} + 4{H^ + }$
The oxidation state of iron in $F{e_2}{O_3}$ is +3.
Rust is an iron oxide. It appears as reddish brown oxide which is formed by the reaction of iron and oxygen in the presence of water or air moisture.
Rust has hydrated iron(III) oxides \[F{e_2}{O_3}\cdot{H_2}O\] and iron(III) oxide-hydroxide \[\left( {FeO\left( {OH} \right),{\text{ }}Fe{{\left( {OH} \right)}_3}} \right)\]. It is associated with the corrosion of refined iron.

So, the correct answer is Option B .

Note:
We have to know that Rust is permeable to air and water, thus, the interior metallic iron underneath a rust layer carries on corroding. Rust prevention needs coatings which preclude formation of rust. Rusting of iron could be prevented by galvanization, cathodic protection, coatings and painting. Rust removal from small iron or steel objects by electrolysis could be done in a home workshop with the help of simple materials.