The smelting of iron in a blast furnace involves, which of the following process(es)?

Options

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

Answer

To solve the question regarding the processes involved in the smelting of iron in a blast furnace, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding Smelting**:
- Smelting is the process of extracting metal from its ore by heating and melting. In the case of iron, the ore is primarily iron oxide (Fe2O3 or Fe3O4).

2. **Role of the Blast Furnace**:
- The blast furnace is a large structure where the smelting process occurs. It operates at high temperatures, typically around 823 Kelvin.

3. **Combustion Process**:
- The process begins with the combustion of coke (a form of carbon) in the presence of hot air. This combustion produces carbon dioxide (CO2) and releases heat, which is essential for the smelting process.

4. **Reduction Process**:
- The high temperature in the furnace allows the carbon dioxide to react with more coke, reducing it to carbon monoxide (CO). This carbon monoxide is a crucial reducing agent that helps convert iron oxides into iron.
- The reduction reactions can be summarized as follows:
- Fe2O3 + 3CO → 2Fe + 3CO2 (Reduction of iron oxide to iron)
- Fe3O4 + 4CO → 3Fe + 4CO2

5. **Slag Formation**:
- During the smelting process, impurities in the ore combine with flux (such as limestone) to form slag. This slag is less dense than molten iron and floats on top, allowing for easy separation.
- The formation of slag can be represented as:
- Impurities + Flux → Slag

6. **Exclusion of Sublimation**:
- Sublimation refers to the transition of a substance from solid to gas without passing through a liquid state. In the context of iron smelting, sublimation does not occur, as the processes involve solid, liquid, and gas phases, but not direct solid-to-gas transitions.

### Conclusion:
Based on the above processes, the smelting of iron in a blast furnace involves:
- **Combustion**
- **Reduction**
- **Slag Formation**

The correct answer to the question is that the smelting of iron involves combustion, reduction, and slag formation, but **not sublimation**.