Question

Zone refining is a method to obtain:
A. very high temperature
B. ultrapure Al
C. ultrapure metals
D. ultrapure oxides

Answer 1

Hint: Pure germanium and silicon can be obtained by metallurgy process. The metallurgy process includes zone refining technique. In this technique the impurities are settled at one end of the metal block so that the rest of the block can be purified.

Complete step by step answer:
Zone refining is the method used for the purification of metals from their ores. The technique zone refining is also known as zone melting or floating zone process.
Principle of zone refining:
The technique zone refining works on the principle that the ore of the given metal is more soluble in molten state as compared to its solid state.
Process:
In this process, a circular heater is placed at the one side of the metal rod. The metal rod is of impure metal. The circular heater proceeds towards the metal rod. Due to the heat, the impurities present in the metal melt. The melted impurities now move with the heater. The pure metal is thus left behind to solidify.
With the moving heater, the concentration of impurities in the molten state increases as the impurities are more soluble in their molten state. At last the impurities get settled at one end of the rod. This process is repeated several times and after that the end of the rod is removed and pure metal is obtained.
Thus, the zone refining is a method to obtain ultrapure metals.
Therefore, the correct option is C.


Note:
The ratio of impurities present in solid state to the impurities present in molten state is known as segregation coefficient. In zone refining the segregation coefficient is mostly less than 1.