Question

Explain zone refining process with an example using the ellingham diagram given below

Answer 1

Answer:

Principle - The impurities in the molten state are more soluble than in the solid state of the metal .

Method - In this method , 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 ,pure metal crystallizes out of the melt and the impurities pass on into the adjacent molten zone. The process is repeated several times and heater is moved in the same direction. At one end ,impurities gets concentrated .This end is cut off.This method is very useful for producing semi-conductors and other metals of very high purity.

eg- B,Si,Ge,In,Ga ,etc

Answer 2

Explanation:

(i) Zone refining is based on the principles of fractional crystallisation. (ii) When an impure metal is melted and allowed solidify, the impurities will prefer to be in the molten region. (iii) In this process the impure metal is taken in the form of a rod.