Amongest the following, how many ores are roasted to convert them into their corresponding metal oxides, alumina, zinc blende, iron pyrites, copper pyrites, galena.

Explanation

To solve the question of how many ores among the given list are roasted to convert them into their corresponding metal oxides, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Process of Roasting**:
- Roasting is a metallurgical process involving heating sulfide ores in the presence of excess air below their melting point. This process converts sulfide ores into their corresponding metal oxides.

2. **Identify the Ores**:
- The ores given in the question are:
- Alumina
- Zinc blende
- Iron pyrites
- Copper pyrites
- Galena

3. **Analyze Each Ore**:
- **Alumina**: This is not a sulfide ore; it is an oxide of aluminum (Al₂O₃). Therefore, it is not roasted.
- **Zinc Blende (ZnS)**: This is a sulfide ore of zinc and is roasted to convert it into zinc oxide (ZnO).
- **Iron Pyrites (FeS₂)**: This is a sulfide ore of iron and is roasted to convert it into iron oxide (Fe₂O₃).
- **Copper Pyrites (CuFeS₂)**: This is a sulfide ore of copper and iron, and it is roasted to convert it into copper oxide (Cu₂O) and iron oxide (Fe₂O₃).
- **Galena (PbS)**: This is a sulfide ore of lead and is roasted to convert it into lead oxide (PbO).

4. **Count the Ores that are Roasted**:
- From the analysis:
- Zinc Blende: Roasted
- Iron Pyrites: Roasted
- Copper Pyrites: Roasted
- Galena: Roasted
- Alumina: Not roasted
- Therefore, the ores that are roasted are Zinc Blende, Iron Pyrites, Copper Pyrites, and Galena.

5. **Conclusion**:
- The total number of ores that are roasted to convert them into their corresponding metal oxides is **4**.

### Final Answer:
**4 ores are roasted to convert them into their corresponding metal oxides.**