Highly electropositive metals can not be extracted by carbon reduction process because these :

Options

A. Metals combine with carbon to form carbides
B. Metals do not react with carbon
C. Metal oxides are not reduced by carbon
D. Loss of metal is more by vaporisation

Answer

To answer the question of why highly electropositive metals cannot be extracted by the carbon reduction process, we can break down the reasoning into clear steps:

### Step-by-Step Solution:

1. **Understanding Highly Electropositive Metals**:
- Highly electropositive metals are those that have a strong tendency to lose electrons and form positive ions. Examples include sodium (Na), potassium (K), and aluminum (Al).

2. **Carbon Reduction Process**:
- The carbon reduction process involves using carbon (usually in the form of coke) to reduce metal oxides to their corresponding metals. This typically requires high temperatures to facilitate the reaction.

3. **High Temperature Requirement**:
- For highly electropositive metals, the temperatures required to reduce their oxides using carbon are extremely high. This is because these metals are very stable in their oxidized forms and require significant energy to break these bonds.

4. **Formation of Metal Carbides**:
- At these high temperatures, instead of reducing to the free metal, highly electropositive metals tend to react with carbon to form metal carbides. For example, sodium can react with carbon to form sodium carbide (Na2C2), which means the metal is not obtained in its elemental form.

5. **Vaporization of Metals**:
- Additionally, the high temperatures involved in the carbon reduction process can lead to the vaporization of the metal. This means that even if some metal were to be produced, a significant amount could be lost as vapor due to the extreme heat.

6. **Conclusion**:
- Therefore, the main reasons highly electropositive metals cannot be extracted by carbon reduction are:
- They combine with carbon to form carbides.
- There is a significant loss of metal due to vaporization at high temperatures.

### Final Answer:
The correct options for the question are:
- **A. Metals combine with carbon to form carbides.**
- **D. Loss of metal is more by vaporization.**