Process of zone refining is used in the purification of

The correct answer is Option (3) → Ge

Zone refining is based on the principle that impurities are more soluble in the melt than in the solid metal. A mobile heater moves a molten zone along a rod of the impure metal; pure metal crystallises behind it and the impurities move on with the melt to one end, which is cut off. The method gives metals of very high purity and is used for semiconductors such as germanium, silicon, boron, gallium and indium.

Note 1: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Refining – “… Zone refining: This method is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal. A circular mobile heater is fixed at one end of a rod of the impure metal. The molten zone moves along with the heater which is moved forward. As the heater moves forward, the pure metal crystallises out of the melt and the impurities pass on into the adjacent molten zone. The process is repeated several times and the heater is moved in the same direction. At one end, impurities get concentrated. This end is cut off. This method is very useful for producing semiconductor and other metals of very high purity, e.g., germanium, silicon, boron, gallium and indium.”

Note 2: The same/similar question has been asked in different years by NTA as per the details given below: