`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. In the laboratory, `MnO_(2)` is made by:

Options

A. heating Mn in `O_(2)`
B. oxidising `Mn^(2+)` in air
C. electrolytic oxidation of `MnSO_(4)`
D. precipitating `MnO_(2)` from solution when performing titration of `KMnO_(4)` in alkaline medium

Answer

To prepare manganese dioxide (MnO₂) in the laboratory, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**: The primary reactants needed for the preparation of MnO₂ are potassium permanganate (KMnO₄) and manganese(II) sulfate (MnSO₄).

2. **Set Up the Reaction**: The reaction can be represented as follows:
\[ 2 KMnO_4 + 5 MnSO_4 + 8 H_2O \rightarrow 6 MnO_2 + K_2SO_4 + 5 H_2SO_4 \]
This equation shows that potassium permanganate reacts with manganese(II) sulfate and water to produce manganese dioxide, potassium sulfate, and sulfuric acid.

3. **Perform the Titration**: In the laboratory, the reaction is typically carried out in an alkaline medium. You would titrate KMnO₄ with MnSO₄ in the presence of water to facilitate the reaction.

4. **Precipitation of MnO₂**: During the reaction, manganese dioxide (MnO₂) precipitates out of the solution as a brown solid. This is the desired product.

5. **Collect and Purify MnO₂**: Once the reaction is complete, the MnO₂ precipitate can be collected by filtration. It may be washed to remove any impurities and dried for further use.

### Final Answer:
In the laboratory, MnO₂ is prepared by precipitating MnO₂ from a solution when performing titration of potassium permanganate (KMnO₄) in an alkaline medium.

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