In the preparation of KMnO4, pyrolusite `(MnO_(2))` is first converted to potassium magnate `(K_(2)MnO_(4))`. In this conversion, the oxidation state of manganese changes from 

Options

A. `+1" to "+3`
B. `+2" to "+4`
C. `+3" to "+5`
D. `+4" to "+6`

Answer

To determine the change in the oxidation state of manganese when pyrolusite (MnO₂) is converted to potassium manganate (K₂MnO₄), we can follow these steps:

### Step 1: Identify the oxidation state of manganese in MnO₂
- The formula for manganese dioxide is MnO₂.
- Oxygen has an oxidation state of -2.
- Let the oxidation state of manganese (Mn) be represented as X.
- The compound is neutral, so the sum of oxidation states must equal zero.

**Equation:**
\[ X + 2(-2) = 0 \]
\[ X - 4 = 0 \]
\[ X = +4 \]

**Conclusion:**
The oxidation state of manganese in MnO₂ is +4.

### Step 2: Identify the oxidation state of manganese in K₂MnO₄
- The formula for potassium manganate is K₂MnO₄.
- Potassium (K) has an oxidation state of +1 and there are 2 potassium atoms, contributing +2.
- Oxygen has an oxidation state of -2, and there are 4 oxygen atoms, contributing -8.
- Let the oxidation state of manganese (Mn) in K₂MnO₄ be represented as Y.

**Equation:**
\[ 2(+1) + Y + 4(-2) = 0 \]
\[ 2 + Y - 8 = 0 \]
\[ Y - 6 = 0 \]
\[ Y = +6 \]

**Conclusion:**
The oxidation state of manganese in K₂MnO₄ is +6.

### Step 3: Determine the change in oxidation state
- The oxidation state of manganese changes from +4 in MnO₂ to +6 in K₂MnO₄.

**Final Conclusion:**
The change in oxidation state of manganese during the conversion from MnO₂ to K₂MnO₄ is from +4 to +6.

### Answer:
The oxidation state of manganese changes from +4 to +6.

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