When `MnO_2` is fused with KOH and `KNO_3` , a coloured compound is formed. Choose the right compound with the appropriate colour.

Options

A. `K_2MnO_4` , green
B. `KMnO_4` purple
C. `Mn_2O_3` , brown
D. `Mn_3O_4` black

Explanation

To solve the question regarding the reaction of MnO2 with KOH and KNO3, we can follow these steps:

### Step 1: Identify the Reactants
We have three reactants:
- Manganese dioxide (MnO2)
- Potassium hydroxide (KOH)
- Potassium nitrate (KNO3)

### Step 2: Understand the Reaction
When MnO2 is fused with KOH and KNO3, a reaction occurs that leads to the formation of a colored compound. The fusion process typically involves heating the reactants together, which allows them to react chemically.

### Step 3: Write the Reaction Equation
The reaction can be represented as:
\[ \text{MnO}_2 + 4 \text{KOH} + 2 \text{KNO}_3 \rightarrow 2 \text{K}_2\text{MnO}_4 + 2 \text{KNO}_2 + 2 \text{H}_2\text{O} \]

### Step 4: Identify the Product
From the reaction, we can see that the main product formed is potassium manganate, which is represented as K2MnO4.

### Step 5: Determine the Color of the Product
K2MnO4 is known to be a colored compound. Specifically, it is characterized by its green color.

### Step 6: Conclusion
Thus, the correct compound formed when MnO2 is fused with KOH and KNO3 is K2MnO4, and its appropriate color is green.

### Final Answer
The right compound is K2MnO4 and the color is green.

---