Which of the following metals form amphoteric oxide?

Options

A. Copper
B. Silver
C. Aluminium
D. Iron

Explanation

To determine which of the following metals forms an amphoteric oxide, we need to understand what amphoteric oxides are. Amphoteric oxides are oxides that can react with both acids and bases, producing salt and water in both cases.

### Step-by-Step Solution:

1. **Identify the Metals and Their Oxides**:
- We need to consider the metals provided in the question. Let's assume the metals are Copper (Cu), Silver (Ag), Aluminium (Al), and Iron (Fe).

2. **Check Copper (Cu)**:
- Copper forms Copper(II) oxide (CuO).
- When CuO reacts with an acid (e.g., HCl), it forms CuCl2 (salt) and water.
- However, CuO does not react with bases (e.g., NaOH).
- Conclusion: CuO is a basic oxide, not amphoteric.

3. **Check Silver (Ag)**:
- Silver forms Silver(I) oxide (Ag2O).
- Ag2O reacts with acids to form AgCl (salt) and water.
- It does not react with bases.
- Conclusion: Ag2O is also a basic oxide, not amphoteric.

4. **Check Aluminium (Al)**:
- Aluminium forms Aluminium oxide (Al2O3).
- Al2O3 reacts with acids (e.g., HCl) to produce AlCl3 (salt) and water.
- Al2O3 also reacts with bases (e.g., NaOH) to produce sodium aluminate (NaAlO2) and water.
- Conclusion: Al2O3 is an amphoteric oxide.

5. **Check Iron (Fe)**:
- Iron can form Ferric oxide (Fe2O3).
- Fe2O3 reacts with acids to form FeCl3 (salt) and water.
- However, Fe2O3 does not react with bases.
- Conclusion: Fe2O3 is a basic oxide, not amphoteric.

### Final Conclusion:
Among the metals considered, **Aluminium (Al)** is the only metal that forms an amphoteric oxide (Al2O3).

### Answer:
**Aluminium (Al) forms an amphoteric oxide.**