Which of the following metal oxides are reduced by self-reduction method ?

Options

A. HgO
B. `Cu_2O`
C. PbO
D. `Al_2O_3`

Answer

To determine which metal oxides are reduced by the self-reduction method, we need to analyze the given options based on the properties of the metals involved and their electropositivity.

### Step-by-Step Solution:

1. **Understanding Self-Reduction Method**:
- The self-reduction method is a process where less electropositive metals can reduce their own oxides. This typically involves a reaction where a metal oxide is partially reduced to form the metal and a gaseous product, often sulfur dioxide (SO2).

2. **Analyzing the Options**:
- We have four metal oxides to consider:
- **HgO (Mercury(II) oxide)**
- **Cu2O (Copper(I) oxide)**
- **PbO (Lead(II) oxide)**
- **Al2O3 (Aluminum oxide)**

3. **Evaluating Each Metal Oxide**:
- **HgO**: Mercury is a less electropositive metal. It can undergo self-reduction, where it can reduce itself to elemental mercury (Hg).
- **Cu2O**: Copper is also a less electropositive metal. It can reduce itself in the presence of sulfur compounds, leading to the formation of elemental copper (Cu).
- **PbO**: Lead is another less electropositive metal. It can reduce itself to lead (Pb) through a similar self-reduction process.
- **Al2O3**: Aluminum is a more electropositive metal and does not undergo self-reduction. Instead, it typically requires more energy for reduction, often through electrolysis.

4. **Conclusion**:
- The metal oxides that can be reduced by the self-reduction method are **HgO, Cu2O, and PbO**. Therefore, the correct answer is A (HgO), B (Cu2O), and C (PbO).

### Final Answer:
The metal oxides that are reduced by the self-reduction method are **HgO, Cu2O, and PbO**.