Question

Which is the best method used to obtain pure metals of Ti, Zr, Hf?

• A. Cupellation
• B. Van Arkel Method
• C. Both A & B
• D. None of these

Answer 1

The correct option is B

Van Arkel Method

Cupellation is a method in which impure metal is heated in presence of air, in an oval shaped crucible, during which impurities are oxidized in the form of respective metal oxides. Chances are that some impurities may not be exposed to air and are not converted to metal oxide. Hence it is not a method to obtain ultra pure metals.

Van Arkel Method: The impure metal is converted to volatile compound, impurities being unaffected. Thus formed pure volatile compound is decomposed to get the pure metal. Hence this is a method to obtain ultra pure metal.

For example:

$Zr\left(Impure\right)$ $+2I_2$ $\to$ $Zr{I}_4$ $\left(Gas\right)$

$Zr{I}_4$ $\left(Gas\right)$ $\to$ $Zr\left(Pure\right)+2I_2$