In Mond's process for refining of nickel, the following reactions occur. The value of 'x' is --------.
`Ni+xCOoverset("330 K - 350 K")rarr No(CO)_(x)overset("450 K - 407 K")rarr Ni_((s))+xCO_((g))`

Answer

To solve the problem regarding the value of 'x' in the Mond's process for refining nickel, we can analyze the given reactions step by step.

### Step 1: Understanding the Reaction
In the Mond's process, nickel (Ni) reacts with carbon monoxide (CO) to form a volatile nickel carbonyl compound. The reaction can be represented as:
\[ \text{Ni} + x \text{CO} \rightarrow \text{Ni(CO)}_x \]

### Step 2: Identifying the Compound
From the video transcript, we learn that the compound formed is nickel carbonyl, specifically \( \text{Ni(CO)}_4 \). This indicates that the value of 'x' corresponds to the number of CO molecules that bond with one nickel atom.

### Step 3: Determining the Value of 'x'
Since the compound formed is \( \text{Ni(CO)}_4 \), it is clear that:
\[ x = 4 \]

### Step 4: Final Reaction
The next part of the process involves heating the nickel carbonyl to decompose it back into solid nickel and carbon monoxide gas:
\[ \text{Ni(CO)}_4 \rightarrow \text{Ni}_{(s)} + 4 \text{CO}_{(g)} \]

### Conclusion
Thus, the value of 'x' in the reaction is:
\[ \boxed{4} \]

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