Question

In the Van Arkel method for refining zirconium or titanium, the halogen used is?
(A) fluorine
(B) chlorine
(C) bromine
(D) iodine

Answer 1

Hint: The halogen used in the Van Arkel method for refining zirconium and titanium is a black solid at room temperature and when kept in an open vessel, it sublimes to violet-colored irritating vapors. It forms a volatile compound with metal.

Complete step by step solution:
The Van Arkel method is a metallurgical method used to refine zirconium and titanium metal. The main impurity which is to be removed in this refining consists of oxygen and nitrogen.
These impurities are removed by heating the zirconium or titanium metal in an evacuated vessel containing iodine.
\[
   \text{Ti}+2{{\text{I}}_{2}}\xrightarrow{250{}^\circ \text{C}}\text{Ti}{{\text{I}}_{4}} \\
   \\
\]
The metal then reacts with iodine to form metal iodide which is very volatile in nature and impurities remain in the vessel as they cannot react with iodine. So, the metal iodide is volatilized and then is heated on a tungsten filament.
\[\text{Ti}{{\text{I}}_{4}}\xrightarrow[\text{Tungsten filament}]{1400{}^\circ \text{C}}\text{Ti}+2{{\text{I}}_{2}}\]
On heating over a tungsten filament at around $1400{}^\circ \text{C}$ temperature, the metal iodide decomposes to give pure metal and iodine. This iodine produced can then be reused for another round of refining.

Hence, the correct answer is (D) iodine.

Note: The Van Arkel method is based on the principle of thermal decomposition of the metal components. The decomposition of a compound into its different constituents by the action of heat is known as thermal decomposition.