Question

Discuss electrochemical principle regarding rusting of iron.

Hint:

Rusting is an electrochemical process involving the oxidation of iron and reduction of oxygen.

Answer 1

Step 1: Understanding Rusting.
Rusting is an electrochemical process in which iron (Fe) undergoes oxidation in the presence of water and oxygen. This leads to the formation of iron oxides, commonly known as rust. The process of rusting is a corrosion reaction involving both oxidation and reduction.
Step 2: Electrochemical Reactions in Rusting.
The rusting process can be broken down into two half-reactions:
- Oxidation half-reaction (Anode):
At the anode, iron (Fe) loses electrons and is oxidized to iron ions (Fe²⁺). The reaction at the anode is: \[ \text{Fe} \rightarrow \text{Fe}^{2+} + 2e^- \]
- Reduction half-reaction (Cathode):
At the cathode, oxygen from the air reacts with water to form hydroxide ions (OH⁻). The reaction is: \[ \text{O}_2 + 2\text{H}_2\text{O} + 4e^- \rightarrow 4\text{OH}^- \]
Step 3: Formation of Rust.
The Fe²⁺ ions produced at the anode combine with oxygen and water to form iron oxides, commonly Fe₂O₃·xH₂O, which is rust. The process can be represented by: \[ 4\text{Fe}^{2+} + O_2 + 2H_2O \rightarrow 2\text{Fe}_2\text{O}_3 \cdot 2H_2O \] This shows the electrochemical nature of rusting, where iron acts as the anode and oxygen acts as the cathode.