The equivalent mass of potassium permanganate in alkaline medium is

Options

A. Molar mass /2
B. Molar mass / 5
C. Molar mass itself
D. Molar mass/3

Answer

To find the equivalent mass of potassium permanganate (KMnO4) in alkaline medium, we can follow these steps:

### Step 1: Determine the Molar Mass of KMnO4
The molar mass of KMnO4 can be calculated by adding the atomic masses of its constituent elements:
- Potassium (K): 39.1 g/mol
- Manganese (Mn): 54.9 g/mol
- Oxygen (O): 16.0 g/mol (and there are 4 oxygen atoms)

So, the molar mass of KMnO4 is:
\[ \text{Molar Mass} = 39.1 + 54.9 + (4 \times 16.0) \]
\[ \text{Molar Mass} = 39.1 + 54.9 + 64.0 = 158.0 \, \text{g/mol} \]

### Step 2: Determine the n Factor
In alkaline medium, KMnO4 is reduced to MnO2. The oxidation state of manganese in KMnO4 is +7, and in MnO2 it is +4. The change in oxidation state is:
\[ \text{Change} = +7 \text{ (in KMnO4)} - +4 \text{ (in MnO2)} = 3 \]
This means that 3 electrons are gained during the reduction process. Therefore, the n factor for KMnO4 in alkaline medium is 3.

### Step 3: Calculate the Equivalent Mass
The equivalent mass can be calculated using the formula:
\[ \text{Equivalent Mass} = \frac{\text{Molar Mass}}{n \text{ factor}} \]
Substituting the values we have:
\[ \text{Equivalent Mass} = \frac{158.0 \, \text{g/mol}}{3} \]
\[ \text{Equivalent Mass} = 52.67 \, \text{g/equiv} \]

### Conclusion
The equivalent mass of potassium permanganate (KMnO4) in alkaline medium is approximately **52.67 g/equiv**.

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