The method of zone refining of metals is based on the principle of:
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 state
Greater mobility of the pure metal than that of the impurity
Higher melting point of the impurity than that of the pure metal
The correct answer is 2) Greater solubility of the impurity in the molten state than in the solid state.
Zone refining is a purification method based on the principle that impurities are more soluble in the molten state of the material than in the solid state. By creating a molten zone and moving it through a solid metal rod, impurities are selectively dissolved in the molten zone and then moved to one end of the rod, resulting in a more purified metal.