Pure `O_(2)` instead of air is used to oxidise the pig iron because:

Options

A. Molten metal took up small amount of nitrogen which makes the steel brittle
B. Air is not as efficient to oxidise all the impurities to their respective oxides
C. Air contains moisture and will precipitate iron as `Fe_(2)O_(3)`
D. Iron reacts with air to `FeCO_(3)`

Answer

To answer the question "Pure O₂ instead of air is used to oxidize the pig iron because:", we can break down the reasoning into a step-by-step explanation.

### Step-by-Step Solution:

1. **Understanding Pig Iron**:
- Pig iron is an intermediate product in the production of steel, obtained by smelting iron ore. It contains a high carbon content and is not pure iron.

2. **Composition of Air**:
- Air is composed of various gases, primarily nitrogen (N₂), oxygen (O₂), and a small amount of other gases like carbon dioxide (CO₂) and water vapor.

3. **Effects of Nitrogen in Air**:
- When pig iron is oxidized using air, the nitrogen present in the air can react with the iron. However, nitrogen does not oxidize iron effectively; instead, it forms nitrides or creates voids within the iron structure.

4. **Consequences of Using Air**:
- The presence of nitrogen can lead to the formation of voids in the pig iron, which can make the resulting steel brittle. This brittleness is undesirable in steel production as it affects the material's strength and durability.

5. **Advantages of Using Pure O₂**:
- By using pure oxygen (O₂) instead of air, we eliminate the nitrogen and other gases that can interfere with the oxidation process. Pure O₂ allows for a more efficient oxidation of the pig iron, leading to a higher quality product without the brittleness caused by nitrogen.

6. **Conclusion**:
- Therefore, pure O₂ is preferred for oxidizing pig iron because it avoids the introduction of nitrogen, which can create voids and make the steel brittle. This results in a more effective oxidation process and a better quality steel product.

### Final Answer:
Pure O₂ is used instead of air to oxidize pig iron because nitrogen in the air can create voids in the iron, making it brittle. Pure O₂ allows for better oxidation without the negative effects of nitrogen.

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