Monds process is used for the purification of ____________.

The Mond process is used for the purification of nickel.

Explanation:
The Mond process, also known as the carbonyl process, involves the following steps:

Formation of Nickel Carbonyl: Impure nickel is reacted with carbon monoxide (CO) at a temperature of about 50-60°C to form nickel carbonyl (Ni(CO)₄), a gaseous compound:

\text{Ni}_{(s)} + 4 \text{CO}_{(g)} \rightarrow \text{Ni(CO)}_4_{(g)}
Separation of Impurities: The nickel carbonyl is a volatile compound and can be separated from other impurities that do not form carbonyls.

Decomposition: The nickel carbonyl is then heated to a higher temperature (around 200-250°C) to decompose back into pure nickel and carbon monoxide:

\text{Ni(CO)}_4_{(g)} \rightarrow \text{Ni}_{(s)} + 4 \text{CO}_{(g)}
Recycling: The carbon monoxide produced can be recycled back into the process.

The Mond process is effective for purifying nickel because it allows for the separation of nickel from other metals and impurities present in the ore, resulting in high-purity nickel.