Question

Zone refining is based on the principle that ___________.

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

Answer 1

The correct option is B

impurities are more soluble in molten metal than in solid metal.

The zone refining process works on the principle that impurities are more soluble in molten metal than solid metal.

• Zone refining is a process used to separate pure metal from impurities. In this process, a narrow rod of metal is placed inside a movable heater. The heater moves up and down across the rod, each time melting at just one particular cross-sectional area of the rod known as zone.
• In the zone refining process, impurities present in the metal dissolve readily in the molten metal and this molten metal-containing impurity travels from the start position to the end position.
• At the end of the zone refining process, all the impurities settle at the bottom part of the rod and this part of the rod containing maximum impurities is cut and separated from the pure metal rod.

Zone refining is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal. This method is very useful for producing semiconductor and other metals of very high purity, e.g., germanium, silicon, boron, gallium and indium.

So, the correct answer is option (B).