Zone refining is based on the principle that

Options

A. impurities of low boiling metals can be separated by distillation
B. impurities are more soluble in molten metal than in solid metal.
C. different components of a mixture are differently adsorbed on an adsorbent.
D. vapours of volatile compound can be decomposed to give pure metal.

Explanation

**Step-by-Step Solution:**

1. **Understanding Zone Refining**: Zone refining is a purification technique used primarily for metals and semiconductors. It is particularly effective in removing impurities from materials.

2. **Principle of Zone Refining**: The fundamental principle behind zone refining is that impurities tend to be more soluble in the molten state of the metal than in its solid state. This means that when the metal is melted, the impurities dissolve more readily in the liquid form.

3. **Process Description**: In the zone refining process, a circular heater is used to create a molten zone along a solid piece of the impure metal. As the heater moves along the metal, it melts a small region of the metal.

4. **Separation of Impurities**: As the molten zone moves, the impurities that are more soluble in the molten metal migrate into the liquid phase. When the molten zone solidifies, the impurities are left behind in the solid metal, allowing for a purer solid to be obtained.

5. **Cooling and Collection**: After the molten zone has moved through the entire length of the metal, the metal is allowed to cool down. The result is a solid metal that is significantly purer than the original impure metal.

6. **Conclusion**: Therefore, the principle that zone refining is based on is that impurities are more soluble in the molten metal than in the solid metal.

**Final Answer**: Zone refining is based on the principle that impurities are more soluble in the molten metal than in the solid metal.

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