Standard electrode potential of Zn and Fe are known to be (i) -0.76V and (ii) -0.44V respectively. How does it explain that galvanization prevents rusting of iron while zinc slowly dissolves away

Options

A. Since (i) is less than (ii), zinc becomes the cathode and iron the anode
B. Since (i) is less than (ii), zinc becomes the anode and iron the cathode
C. Since (i) is more than (ii), zinc becomes the anode and iron the cathode
D. Since (i) is more than (ii), zinc becomes the cathode and iron the anode

Answer

To understand how galvanization prevents rusting of iron while zinc slowly dissolves away, we need to analyze the standard electrode potentials of zinc (Zn) and iron (Fe) and their roles in electrochemical reactions.

### Step-by-Step Solution:

1. **Identify the Standard Electrode Potentials:**
- The standard electrode potential of zinc (Zn) is -0.76 V.
- The standard electrode potential of iron (Fe) is -0.44 V.

2. **Understanding Electrode Potentials:**
- A more negative electrode potential indicates a greater tendency to lose electrons (oxidation).
- Zinc, with a potential of -0.76 V, is more likely to oxidize compared to iron, which has a potential of -0.44 V.

3. **Electrochemical Reaction:**
- In a galvanic cell, zinc acts as the anode and iron acts as the cathode.
- At the anode (zinc), the oxidation reaction occurs:
\[ \text{Zn} \rightarrow \text{Zn}^{2+} + 2e^- \]
- At the cathode (iron), the reduction reaction occurs:
\[ \text{Fe}^{2+} + 2e^- \rightarrow \text{Fe} \]

4. **Galvanization Process:**
- When zinc is coated on iron, it serves as a sacrificial anode.
- Zinc will oxidize preferentially to iron, thus protecting the iron from rusting (corrosion).
- As zinc oxidizes, it forms a layer of zinc oxide, which protects the underlying iron from moisture and oxygen.

5. **Dissolution of Zinc:**
- Although zinc slowly dissolves away, it does so at a rate that is sufficient to protect the iron underneath.
- The continuous oxidation of zinc prevents the iron from losing electrons and undergoing oxidation (rusting).

6. **Conclusion:**
- The galvanization process effectively prevents rusting of iron because zinc, being more reactive (more negative potential), sacrifices itself to protect iron.