(vi) Which element is purified by zone refining ?

Options

A. Ge
B. Si
C. Sn
D. Ni

Answer

### Step-by-Step Solution:

1. **Understanding Zone Refining**: Zone refining is a metallurgical process used to purify metals, particularly semiconductors. It involves melting a small region of a solid metal and allowing impurities to migrate into the molten zone.

2. **Identifying Suitable Elements**: The process is particularly effective for elements that are semiconductors. The most common elements purified by zone refining are silicon (Si) and germanium (Ge).

3. **Mechanism of Zone Refining**: In zone refining, a circular mobile heater is used to create a molten zone on a solid metal rod. As the heater moves along the rod, the impurities, which are more soluble in the molten state than in the solid state, migrate into the molten zone.

4. **Repetition of the Process**: This heating and movement of impurities is repeated several times. Each time the heater moves, more impurities are drawn into the molten zone, allowing for a gradual increase in the purity of the metal.

5. **Final Purification**: After several passes of the heater, the impurities accumulate at one end of the rod. This end can then be cut off, resulting in a highly purified metal.

### Conclusion:
The elements that are purified by zone refining are **silicon (Si)** and **germanium (Ge)**.

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