Passivity of iron is due to formation of:

Options

A. `Fe_(2)O_(3)`
B. `Fe_(3)O_(4)`
C. `FeSO_(4)`
D. None of these

Answer

To solve the question regarding the passivity of iron, we need to understand the concept of passivity and the chemical processes involved.

### Step-by-Step Solution:

1. **Understanding Passivity of Iron**:
- Passivity refers to the phenomenon where a metal becomes resistant to corrosion and does not react with certain reagents. In the case of iron, this occurs when it forms a protective layer on its surface.

2. **Reaction with Concentrated Nitric Acid**:
- When a piece of iron (Fe) is dipped in concentrated nitric acid (HNO3), it undergoes a reaction that leads to the formation of a passive layer. This layer renders the iron inert to further reactions.

3. **Formation of Iron Oxides**:
- Iron can react with oxygen in the air, leading to the formation of iron oxides. The most relevant oxides in this context are Fe2O3 (iron(III) oxide) and Fe3O4 (iron(II,III) oxide).

4. **Identifying the Correct Oxide**:
- Among the options provided:
- Option 1: Fe2O3
- Option 2: Fe3O4
- Option 3: FeSO4
- Option 4: None of these
- The oxide that is primarily responsible for the passivity of iron is Fe3O4. This oxide forms a protective layer that prevents further corrosion.

5. **Conclusion**:
- Therefore, the passivity of iron is due to the formation of Fe3O4, making option 2 the correct answer.

### Final Answer:
The passivity of iron is due to the formation of Fe3O4.

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