`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 Reaction**: The preparation of MnO₂ can be achieved through the titration of potassium permanganate (KMnO₄) in an alkaline medium. This reaction involves the reduction of KMnO₄.

2. **Write the Balanced Chemical Equation**: The balanced equation for the reaction is:
\[ 2 \text{KMnO}_4 + 3 \text{MnSO}_4 + 2 \text{H}_2\text{O} \rightarrow 5 \text{MnO}_2 + K_2\text{SO}_4 + 4 \text{H}_2\text{O} \]

3. **Prepare the Reaction Mixture**: In the laboratory, prepare a solution of KMnO₄ and add it to a solution containing MnSO₄. Ensure that the medium is alkaline, which can be achieved by adding a base such as sodium hydroxide (NaOH).

4. **Conduct the Titration**: Slowly add the KMnO₄ solution to the MnSO₄ solution while stirring. The KMnO₄ will oxidize Mn²⁺ ions from MnSO₄ to form MnO₂, which will precipitate out of the solution.

5. **Isolate MnO₂**: After the reaction is complete, filter the mixture to separate the solid MnO₂ from the liquid. Wash the precipitate with distilled water to remove any impurities.

6. **Dry the Product**: Finally, dry the MnO₂ precipitate in an oven or air dry it to obtain the final product.

### Final Answer:
In the laboratory, MnO₂ is made by precipitating it from a solution during the titration of KMnO₄ in an alkaline medium.

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