If a metal has low oxygen affinity then the purification of metal may be carried out by :

Options

A. liquation
B. distillation
C. zone refining
D. cupellation

Answer

To solve the question, "If a metal has low oxygen affinity then the purification of metal may be carried out by:", we will analyze the options provided and determine the correct method for purification based on the metal's properties.

### Step-by-Step Solution:

1. **Understanding the Concept of Oxygen Affinity**:
- Metals with low oxygen affinity do not easily react with oxygen. This means that during purification processes, they are less likely to form oxides.

2. **Evaluating the Options**:
- The question suggests several methods for purification. We will evaluate each method to see if it is suitable for a metal with low oxygen affinity.

3. **Option 1: Liquefaction**:
- Liquefaction involves heating the ore until the metal melts, allowing it to flow away from impurities. Since there is no significant interaction with oxygen in this process, it can be used for metals with low oxygen affinity. However, it is not the most common method for purification.

4. **Option 2: Distillation**:
- Distillation is based on differences in boiling points. If the metal has a lower boiling point than its impurities, it can be vaporized and collected. This method also does not involve oxygen, making it applicable for metals with low oxygen affinity.

5. **Option 3: Zone Refining**:
- Zone refining is based on fractional crystallization where impurities remain in the molten phase while the pure metal crystallizes. This method is effective for purifying metals but does not involve oxygen.

6. **Option 4: Cupellation**:
- Cupellation is a refining process that involves heating ores or alloys in the presence of air at high temperatures, which allows for the separation of noble metals from impurities. For example, in the case of silver (Ag) with lead (Pb) impurities, lead reacts with oxygen to form lead oxide (PbO), which can be removed. Since silver has low affinity for oxygen, it remains unaffected during this process.

7. **Conclusion**:
- Among the options evaluated, cupellation is the most suitable method for purifying a metal with low oxygen affinity, as it effectively separates noble metals from their impurities without the metal itself forming oxides.

### Final Answer:
The purification of a metal with low oxygen affinity may be carried out by **cupellation**.

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