Question

Using \( E^\circ \) values of X and Y given below, predict which is better for coating the surface of iron to prevent corrosion and why?
Given: \( E^\circ_{X^{2+}/X} = -2.36 \, \text{V} \) \( E^\circ_{Y^{2+}/Y} = -0.14 \, \text{V} \) \( E^\circ_{Fe^{2+}/Fe} = -0.44 \, \text{V} \)

Hint:

To prevent corrosion, the coating material should have a reduction potential that is less negative than that of the metal being protected, so it will be more stable and less likely to corrode.

Answer 1

1. Predicting the Best Metal for Coating Iron:

Given Data:
- \( E^\circ_{X^{2+}/X} = -2.36 \, \text{V} \)
- \( E^\circ_{Y^{2+}/Y} = -0.14 \, \text{V} \)
- \( E^\circ_{Fe^{2+}/Fe} = -0.44 \, \text{V} \)

Explanation:
The \( E^\circ \) values represent the standard electrode potentials of the half-reactions. The more negative the \( E^\circ \) value, the more easily the substance will undergo oxidation. In the case of corrosion protection, a metal that is more easily oxidized (has a more negative \( E^\circ \)) can protect iron by sacrificing itself and forming a protective coating.

Step 1: Analyzing the Electrode Potentials:
- The more negative the \( E^\circ \) value, the more readily the substance will lose electrons and undergo oxidation. Therefore, the metal with the most negative \( E^\circ \) will be more easily oxidized and form a sacrificial layer to protect iron from corrosion. - Iron (\( Fe^{2+}/Fe \)) has a standard electrode potential of \( -0.44 \, \text{V} \), which means iron can be oxidized in the presence of a more easily oxidized metal.

Step 2: Comparing X and Y for Coating:
- \( E^\circ_{X^{2+}/X} = -2.36 \, \text{V} \): Metal X has a very negative electrode potential, meaning it is highly prone to oxidation. This makes it a good candidate for sacrificial protection. - \( E^\circ_{Y^{2+}/Y} = -0.14 \, \text{V} \): Metal Y has a less negative \( E^\circ \), meaning it is less prone to oxidation compared to metal X.

Conclusion:
Since metal X has a more negative \( E^\circ \) value, it is more likely to undergo oxidation and form a protective sacrificial coating on iron. Thus, metal X is a better choice for coating the surface of iron to prevent corrosion.