The smelting of iron in a blast furnace involves the following processes :

Options

A. combustion
B. reduction
C. slag formation
D. sublimation

Answer

To solve the question about the processes involved in the smelting of iron in a blast furnace, we can break down the steps involved in the smelting process:

### Step-by-Step Solution:

1. **Understanding the Components**:
- The blast furnace operates using three main materials: iron ore (primarily Fe2O3), coke (a form of carbon), and limestone (calcium carbonate).

**Hint**: Identify the key materials used in the process.

2. **Combustion of Coke**:
- The coke is ignited in the presence of oxygen, leading to its combustion. This reaction produces carbon dioxide (CO2):
\[ \text{C (s) + O}_2 \text{(g) } \rightarrow \text{CO}_2 \text{(g)} \]

**Hint**: Look for the reaction that produces carbon dioxide from coke.

3. **Formation of Carbon Monoxide**:
- The carbon dioxide produced can react with more carbon (coke) to form carbon monoxide (CO), which acts as a reducing agent:
\[ \text{CO}_2 \text{(g) + C (s) } \rightarrow 2\text{CO (g)} \]

**Hint**: Identify how carbon dioxide is converted back to carbon monoxide.

4. **Reduction of Iron Ore**:
- The carbon monoxide then reduces iron(III) oxide (Fe2O3) to iron(II, III) oxide (Fe3O4) and carbon dioxide:
\[ \text{Fe}_2\text{O}_3 \text{(s) + 3CO (g) } \rightarrow 2\text{Fe}_3\text{O}_4 \text{(s) + 3CO}_2 \text{(g)} \]
- This reaction occurs at temperatures between 200°C to 700°C.

**Hint**: Focus on how carbon monoxide interacts with iron ore.

5. **Further Reduction**:
- The iron(II, III) oxide (Fe3O4) is further reduced by carbon monoxide to form ferrous oxide (FeO) and more carbon dioxide:
\[ \text{Fe}_3\text{O}_4 \text{(s) + 4CO (g) } \rightarrow 3\text{FeO (s) + 4CO}_2 \text{(g)} \]

**Hint**: Consider the continuation of the reduction process.

6. **Formation of Slag**:
- Limestone (calcium carbonate) decomposes into calcium oxide (CaO) and carbon dioxide (CO2):
\[ \text{CaCO}_3 \text{(s) } \rightarrow \text{CaO (s) + CO}_2 \text{(g)} \]
- The calcium oxide then reacts with impurities (like SiO2) to form slag, which is lighter than molten iron and can be removed:
\[ \text{CaO (s) + SiO}_2 \text{(s) } \rightarrow \text{CaSiO}_3 \text{(l, slag)} \]

**Hint**: Identify the role of limestone in the process.

7. **Final Product**:
- The molten iron (Fe) is collected at the bottom of the furnace, while the slag floats on top and is removed.

**Hint**: Think about the separation of the final products.

### Conclusion:
The smelting of iron in a blast furnace involves the following processes:
- **Combustion** (of coke to form CO2)
- **Reduction** (of iron ore by CO)
- **Slag Formation** (from limestone and impurities)

Therefore, the correct options are A (Combustion), B (Reduction), and C (Slag Formation). Option D (Sublimation) is incorrect as it does not occur in this process.