The refining method used when the metal and the impurities have low and high melting temperatures, respectively, is

Options

A. vapour phase refining
B. liquation
C. zone refining
D. distillation

Answer

To solve the question regarding the refining method used when the metal has a low melting point and the impurities have a high melting point, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Problem**: We need to identify a refining method suitable for a scenario where the metal has a low melting point and the impurities have a high melting point.

2. **Identify the Characteristics of the Metals**:
- The metal in question has a **low melting point**.
- The impurities present have a **high melting point**.

3. **Consider the Refining Methods**:
- Common refining methods include:
- Electrolytic refining
- Distillation
- Liquefaction
- Zone refining

4. **Analyze the Suitable Method**:
- Since the metal has a low melting point, it can be melted easily.
- The impurities, having a high melting point, will remain solid when the metal is melted.
- This suggests that a method which separates based on melting points would be effective.

5. **Choose the Correct Method**:
- The method that allows the metal to be liquefied while keeping the impurities solid is **liquefaction**.
- In liquefaction, the separation is based on differences in melting points and densities, allowing the low melting point metal to be separated from the high melting point impurities.

6. **Final Answer**:
- The refining method used when the metal has a low melting point and the impurities have a high melting point is **liquefaction**.

### Conclusion:
- Therefore, the correct option is **B** (liquefaction).

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