The method of zone refining of metals is based on the principle of:
- Greater mobility of the pure metal than that of the impurity
- Higher melting point of the impurity than that of the pure metal
- Greater noble character of the solid metal than that of the impurity
- Greater solubility of the impurity in the molten state than in the solid
The Correct Option is D
Solution and Explanation
Zone refining involves the use of a circular mobile heater at one end of a rod of impure metal. The heater creates a molten zone that moves along the rod as it is slowly moved forward. As the molten zone advances through the rod, the pure metal crystallizes out of the melt while the impurities are more soluble in the molten state and are carried along with the advancing molten zone. This repeated process of melting and solidifying results in the gradual purification of the metal.
So, the correct answer is (D): Greater solubility of the impurity in the molten state than in the solid
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Concepts Used:
Refining
Refining is an industrial process of reducing the impurities of a substance. In simpler terms, refining is a process of purification of metals to remove the impurities from them to obtain the metals in the purest form.
Refining Methods of Metals
There are various methods used in the refining process of metals. They are listed below-
- Distillation
- Liquidation
- Poling
- Oxidation
- Electrolytic refining
- Zone refining
- Vapour phase refining
- Van-Arkel method
- Chromatographic method
Check: Zone Refining