The correct answer is option 2. Refining of \(Zr\) and \(Ti\).
The van Arkel method is a chemical purification method used for the refining of certain reactive metals, particularly zirconium (\(Zr\)) and titanium (\(Ti\)). The method is based on the formation of volatile metal compounds, which can be decomposed to obtain highly pure metal.
Here's a detailed explanation of the van Arkel method:
1. Formation of Metal Tetraiodide:
The process begins with the formation of metal tetraiodide (\(Ml_4\)) by reacting the metal with iodine. This reaction typically involves heating the metal in a stream of iodine vapor.
The chemical reaction for zirconium (\(Zr\)) is represented as:
\[ Zr + 2I_2 \rightarrow ZrI_4 \]
The metal tetraiodide formed is a volatile compound.
2. Formation of Metal Iodide Complex:
The metal tetraiodide is then vaporized and combined with a more reactive metal, often tantalum (\(Ta\)) or tungsten (\(W\)), which acts as a getter to remove any impurities present.
The getter metal reacts with any remaining impurities to form a non-volatile compound.
The overall reaction can be represented as:
\[ ZrI_4 + 2Ta \rightarrow 2TaI_4 + Zr \]
3. Decomposition to Obtain Pure Metal:
The metal iodide complex is then decomposed to obtain pure metal. This step involves heating the complex to a high temperature, causing the metal to be deposited.
The reaction can be represented as:
\[ 2TaI_4 \rightarrow 2Ta + 4I_2 \]
The impurities remain in the form of non-volatile compounds with the getter metal.
4. Recycling of Iodine:
Iodine, which is released during the decomposition step, can be recovered and reused in the process.
Summary:
The van Arkel method is effective for refining metals with high reactivity, such as zirconium and titanium.
The method relies on the formation of volatile metal compounds, their reaction with a getter metal to remove impurities, and subsequent decomposition to obtain pure metal.
So, the correct answer is 2. Refining of \(Zr\) and \(Ti\). | 
