Disadvantages of using carbon as a reducing agent :

Options

A. High temperature is needed
B. Many metals combine with carbon to form carbides
C. Low temperature is needed
D. Many metals combine with carbon and do not form carbides

Answer

### Step-by-Step Solution:

1. **Understanding Reducing Agents**:
- A reducing agent is a substance that donates electrons to another substance, causing the reduction of that substance while the reducing agent itself gets oxidized. Carbon is often used as a reducing agent in metallurgical processes.

2. **High Temperature Requirement**:
- One major disadvantage of using carbon as a reducing agent is that it requires high temperatures for the reduction process to occur effectively. This is particularly true in processes like the extraction of metals from their ores using a blast furnace.
- **Implication**: The need for high temperatures makes the process expensive due to increased energy costs and the requirement for specialized equipment like blast furnaces.

3. **Formation of Carbides**:
- Another disadvantage is that when carbon is used as a reducing agent, it can react with certain metals to form carbides. For example, metals like magnesium and calcium can form calcium carbide (CaC2) and magnesium carbide.
- **Implication**: The formation of carbides can complicate the extraction process and may lead to the loss of the metal in the form of carbides rather than obtaining the pure metal.

4. **Conclusion**:
- In summary, the two main disadvantages of using carbon as a reducing agent are:
- The requirement for high temperatures which increases costs and complexity.
- The potential for forming carbides with certain metals, which can hinder the extraction of the desired metal.