_____involves treating the powdered ore with a suitable reagent which selectively dissolves the ore but not the impurities.

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Process**: The question asks for a process that involves treating powdered ore with a reagent that selectively dissolves the ore while leaving the impurities behind. This indicates a method of concentrating the ore.

2. **Identifying the Process**: The process that fits this description is known as "leaching." Leaching is a hydrometallurgical method used to extract valuable metals from their ores.

3. **Mechanism of Leaching**: In leaching, the powdered ore is treated with a suitable chemical reagent. This reagent interacts with the ore to form a soluble complex, allowing the metal to dissolve into the solution.

4. **Separation of Impurities**: The impurities present in the ore do not react with the reagent and remain insoluble. As a result, they can be easily washed away, leaving behind a solution containing the dissolved metal.

5. **Examples of Leaching**: Leaching is commonly used in extractive metallurgy for metals such as gold, silver, and aluminum. For instance, in the case of aluminum, the ore bauxite (Al2O3·2H2O) can be treated with a suitable reagent to extract aluminum.

6. **Conclusion**: Therefore, the answer to the question is "leaching," which is the process that involves treating the powdered ore with a suitable reagent that selectively dissolves the ore but not the impurities.

**Final Answer**: Leaching

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