Question

The metal purified by Mond pross is X and metal purified by van Arkel method is Y. X and Y respectively are:

• A. Ni, Zr
• B. Mn, Ti
• C. Zn, Ti
• D. Mn, Ni

Hint:

Purification Methods Summary:

• Mond Process: Used for Ni, based on formation of volatile carbonyls.
• Van Arkel Method: Used for high-purity Ti and Zr, based on volatile iodides.
• Zone refining, Electrolysis, Distillation — other methods for different metals.

Answer 1

The Correct Option is A

Mond Process (for Ni):

• This method involves the conversion of impure nickel into a volatile compound, nickel tetracarbonyl \( \mathrm{Ni(CO)_4} \), at a lower temperature.
• The volatile \( \mathrm{Ni(CO)_4} \) is decomposed at higher temperature to give pure nickel metal.

  \[ \begin{aligned} \mathrm{Ni} + 4\mathrm{CO} &\rightarrow \mathrm{Ni(CO)_4} \quad \text{(at 330 K)} \\ \mathrm{Ni(CO)_4} &\rightarrow \mathrm{Ni} + 4\mathrm{CO} \quad \text{(at 450 K)} \end{aligned} \]

• This process is suitable for purification of nickel due to the volatility of \( \mathrm{Ni(CO)_4} \).

Van Arkel Method (for Zr, Ti):

• This method is used to purify metals like Zirconium (Zr) and Titanium (Ti) which form volatile iodides.
• The impure metal is reacted with iodine to form volatile \( \mathrm{ZrI_4} \), which is then decomposed on a hot tungsten filament to deposit pure Zr.

  \[ \begin{aligned} \mathrm{Zr} + 2 \mathrm{I}_2 &\rightarrow \mathrm{ZrI_4} \quad \text{(volatile)} \\ \mathrm{ZrI_4} &\rightarrow \mathrm{Zr} + 2 \mathrm{I}_2 \quad \text{(on tungsten filament)} \end{aligned} \]

Therefore, the correct pair is:

\[ X = \text{Ni (Mond)}, \quad Y = \text{Zr (Van Arkel)} \]

Answer 2

Step 1: Understanding the Mond Process and its application
The Mond process, also known as the carbonyl process, is a highly efficient method used for the purification of nickel. It involves the reaction of impure nickel with carbon monoxide (CO) at around 50–60°C to form a volatile complex called nickel tetracarbonyl, Ni(CO)₄. This complex is a colorless, volatile liquid that can easily be separated from impurities because most impurities do not form such volatile complexes.

Step 2: Mechanism of the Mond Process
Impure nickel + Carbon monoxide → Nickel carbonyl (Ni(CO)₄) [at ~50–60°C]
The nickel carbonyl is then heated to about 200°C, where it decomposes:
Nickel carbonyl → Pure nickel + Carbon monoxide (recycled)
This thermal decomposition deposits pure nickel onto a heated surface, and the CO gas is recycled to continue the process.

Step 3: Importance of the Mond Process
This process is highly selective and produces nickel of very high purity (up to 99.99%). It is widely used in the industry due to its ability to purify large amounts of nickel efficiently.

Step 4: Understanding the Van Arkel process and its application
The Van Arkel process, also known as the iodide process, is a method used to purify refractory metals such as zirconium (Zr) and titanium (Ti). These metals form volatile tetraiodides (e.g., ZrI₄, TiI₄) upon reaction with iodine.

Step 5: Mechanism of the Van Arkel Process
In this process, impure metal is reacted with iodine at about 200–250°C to form the volatile metal tetraiodide:
Impure metal + Iodine → Metal tetraiodide (volatile)
This volatile compound is then decomposed on a hot filament (usually tungsten) heated to about 1400°C:
Metal tetraiodide → Pure metal (deposited on filament) + Iodine (recycled)

Step 6: Importance of the Van Arkel Process
The Van Arkel process yields extremely pure metals, particularly useful for metals that are difficult to purify by other methods due to their high melting points and chemical reactivity.

Step 7: Conclusion
Thus, the metal purified by the Mond process (X) is nickel (Ni), known for its ability to form nickel carbonyl. The metal purified by the Van Arkel method (Y) is zirconium (Zr), which forms volatile tetraiodides for purification.