Which of the following processes lead to formation of `K_2MnO_4`:

Options

A. Heating of `KMnO_4` with `KOH`
B. Reaction of formaldehyde with `KMnO_4` in presence of conc. `KOH`
C. Reaction of cuprous oxide with alkaline `KMnO_4`solution
D. All of the above

Answer

To determine which processes lead to the formation of \( K_2MnO_4 \), we will analyze each option provided in the question.

### Step 1: Analyze the first process - Heating of \( KMnO_4 \) with \( KOH \)

When potassium permanganate (\( KMnO_4 \)) is heated with potassium hydroxide (\( KOH \)), the reaction can be represented as follows:

\[ 2 KMnO_4 + 2 KOH \rightarrow K_2MnO_4 + 2 H_2O + O_2 \]

In this reaction, \( K_2MnO_4 \) is formed along with water and oxygen gas.

### Step 2: Analyze the second process - Reaction of formaldehyde with \( KMnO_4 \) in the presence of concentrated \( KOH \)

When formaldehyde (\( HCHO \)) reacts with potassium permanganate in the presence of concentrated \( KOH \), the reaction can be represented as:

\[ KMnO_4 + HCHO + KOH \rightarrow K_2MnO_4 + H_2O + CH_2(OH) \]

Here, \( K_2MnO_4 \) is also produced along with water and another product.

### Step 3: Analyze the third process - Reaction of cuprous oxide with alkaline \( KMnO_4 \)

When cuprous oxide (\( Cu_2O \)) reacts with alkaline potassium permanganate, the reaction can be represented as:

\[ Cu_2O + 2 KMnO_4 + 2 KOH \rightarrow 2 K_2MnO_4 + 2 Cu(OH)_2 \]

In this case, \( K_2MnO_4 \) is formed as well.

### Conclusion

From the analysis of all three processes, we can conclude that all of them lead to the formation of \( K_2MnO_4 \).

Thus, the correct answer is:
**All of the above processes lead to the formation of \( K_2MnO_4 \).**

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