`MnO_(2)` is the most important oxide of manganese , `MnO_(2)` occurs natually as the black coloured mineral pyrolusite. It is an oxidising agent, and decomposes to `Mn_(3)O_(4)` on heating to `530^(@)`C. It is used in the preparation of potassium permanaganate and in the productioon of `Cl_(2)` gas. Over half million tonnes per year of `MnO_(2)` is used in dry batteries.
Q. When `MnO_(2)` is fused with KOH in the presence of air, the product formed is:

Options

A. Purple colour `KMnO_(4)`
B. Green colour `K_(2)MnO_(4)`
C. Colourless `MnO_(4)^(-)`
D. None of these

Answer

To solve the question regarding the product formed when `MnO2` is fused with `KOH` in the presence of air, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactants in this reaction are manganese dioxide (`MnO2`), potassium hydroxide (`KOH`), and oxygen from the air.

2. **Understand the Reaction Conditions**: The reaction takes place when `MnO2` is fused with `KOH` in the presence of air. Fusion typically involves heating the reactants to allow them to react.

3. **Write the Reaction**: When `MnO2` reacts with `KOH` in the presence of air, it undergoes a reaction that produces potassium manganate (`K2MnO4`) and water (`H2O`). The balanced chemical equation for this reaction is:
\[ 2 \, MnO_2 + 4 \, KOH + O_2 \rightarrow 2 \, K_2MnO_4 + 2 \, H_2O \]

4. **Identify the Product**: The product formed from this reaction is potassium manganate, which is represented as `K2MnO4`. This compound is known to have a green color.

5. **Check the Options**: The options given in the question are:
- A. Purple color KMnO4
- B. Green color K2MnO4
- C. Colorless MnO4
- D. None of these

Based on our reaction, the correct product is `K2MnO4`, which is green in color.

6. **Conclusion**: Therefore, the correct answer to the question is option B: Green color `K2MnO4`.