Rusting occurs in the presence of water and air.

Iron provides the anodic spot and gets oxidized

The correct answer is option 1. Iron provides the anodic spot and gets oxidized.

Rusting is an electrochemical process that occurs when iron is exposed to water and oxygen over time. The process involves the oxidation of iron and the reduction of oxygen, leading to the formation of rust (hydrated iron(III) oxide).

The Electrochemical Reactions Involved

Rusting can be broken down into two key reactions: the anodic reaction and the cathodic reaction.

Anodic Reaction (Oxidation of Iron)

Where it Occurs: At certain spots on the surface of the iron, known as anodic spots.

What Happens: Iron atoms lose electrons and become iron ions. This process is called oxidation, where iron (Fe) is oxidized to iron(II) ions (\(\text{Fe}^{2+}\)):

\(\text{Fe} \rightarrow \text{Fe}^{2+} + 2e^-\)

Result: The iron at the anodic spot corrodes as it loses electrons. The electrons are then free to move to other areas on the iron surface.

Cathodic Reaction (Reduction of Oxygen)

Where it Occurs: At other spots on the iron surface, known as cathodic spots.

What Happens: The electrons released from the anodic reaction move to the cathodic spots, where they are used to reduce oxygen from the air. The oxygen is dissolved in water and reacts with the electrons and water to form hydroxide ions (\(\text{OH}^-\)):

\(\text{O}_2 + 2\text{H}_2\text{O} + 4e^- \rightarrow 4\text{OH}^-\)

Result: Oxygen acts as the oxidizing agent (gets reduced), and hydroxide ions are formed in the process.

Formation of Rust (Iron(III) Hydroxide)

The iron(II) ions (\(\text{Fe}^{2+}\)) produced in the anodic reaction react with the hydroxide ions (\(\text{OH}^-\)) produced in the cathodic reaction to form iron(II) hydroxide:

\(\text{Fe}^{2+} + 2\text{OH}^- \rightarrow \text{Fe(OH)}_2\)

Further Oxidation: The iron(II) hydroxide is unstable and further reacts with oxygen and water to form iron(III) hydroxide (\(\text{Fe(OH)}_3\)), which then dehydrates to form rust, a hydrated iron(III) oxide

Explanation of the Options

Option 1: Iron provides the anodic spot and gets oxidized.

This is correct. Iron acts as the anode in the rusting process and is oxidized to form iron ions (\(\text{Fe}^{2+}\)).

Option 2: Oxygen provides the anodic spot and gets reduced.

This is incorrect. Oxygen does not provide the anodic spot; instead, it acts as the cathode and undergoes reduction.

Option 3: Iron provides the cathodic spot and gets oxidized.

This is incorrect. Iron provides the anodic spot where it gets oxidized, not the cathodic spot.

Option 4: Oxygen provides the cathodic spot and gets oxidized.

This is incorrect. Oxygen provides the cathodic spot but undergoes reduction, not oxidation.

Conclusion

The correct answer is Option 1: Iron provides the anodic spot and gets oxidized. In the rusting process, iron is oxidized at the anode, while oxygen is reduced at the cathode. This electrochemical reaction leads to the formation of rust on the iron surface.