In the metallurgy of iron, when limestone is added to the blast furnace,the calcium ions end up in

Options

A. Slag
B. Gangue
C. Metallic calcium
D. Calcium carbonate

Explanation

To solve the question regarding the fate of calcium ions when limestone is added to the blast furnace in the metallurgy of iron, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Role of Limestone**:
- Limestone, chemically represented as calcium carbonate (CaCO3), is added to the blast furnace during the iron extraction process.

2. **Decomposition of Limestone**:
- When limestone is heated in the blast furnace, it undergoes thermal decomposition. The reaction can be represented as:
\[ \text{CaCO}_3 (s) \rightarrow \text{CaO} (s) + \text{CO}_2 (g) \]
- This reaction produces lime (CaO) and carbon dioxide (CO2).

3. **Function of Lime (CaO)**:
- The lime (CaO) produced acts as a flux. A flux is a substance that helps to lower the melting point of other materials and aids in the removal of impurities.

4. **Reaction with Silica**:
- In the presence of silica (SiO2), lime reacts to form calcium silicate (CaSiO3). The reaction can be represented as:
\[ \text{CaO} (s) + \text{SiO}_2 (s) \rightarrow \text{CaSiO}_3 (l) \]
- Calcium silicate is a key component of the slag formed during the iron extraction process.

5. **Formation of Slag**:
- The calcium silicate (CaSiO3) formed is less dense than the molten iron and floats on top of it. This mixture of calcium silicate and other impurities is referred to as slag.

6. **Conclusion**:
- Therefore, the calcium ions that originate from the limestone end up in the slag formed during the metallurgy of iron.

### Final Answer:
The calcium ions end up in **slag**.

---