`KMnO_4` reacts with `Na_2S_2O_3` in acidic, strongly basic and aqueous (neutral) media. `100mL` of `LMnO_4` reacts with 100 mL of 0.1 M `Na_2S_2O_3` in acidic, basic and neutral media.
Q. The molarity (M) of `KMnO_4` solution in basic medium is:

Options

A. 0.8 M
B. 0.08 M
C. 0.26 M
D. 0.026 M

Explanation

To find the molarity of the `KMnO4` solution in basic medium, we can follow these steps:

### Step 1: Understand the Reaction
In basic medium, `KMnO4` (potassium permanganate) is reduced from an oxidation state of +7 (Mn) to +6 (Mn). This means that for each mole of `KMnO4`, one electron is gained in the reduction process.

### Step 2: Determine the Value of n
The number of electrons transferred during the reaction is denoted by 'n'. Since `KMnO4` goes from +7 to +6, the value of n is 1.

### Step 3: Write the Equivalent Expressions
We can express the equivalence of the reactants in terms of milliequivalents:
- For `KMnO4`:
\[ \text{Milliequivalents of } KMnO4 = \text{Molarity of } KMnO4 \times n \times \text{Volume in L} \]
- For `Na2S2O3`:
\[ \text{Milliequivalents of } Na2S2O3 = \text{Normality of } Na2S2O3 \times \text{Volume in L} \]

### Step 4: Calculate the Milliequivalents for `Na2S2O3`
Given that the concentration of `Na2S2O3` is 0.1 M and it has a normality factor of 8 (because 2 moles of thiosulfate react with 1 mole of `KMnO4`), we can calculate the milliequivalents:
\[ \text{Milliequivalents of } Na2S2O3 = 0.1 \, \text{N} \times 100 \, \text{mL} = 0.1 \times 1 = 0.1 \, \text{equivalents} \]

### Step 5: Set Up the Equation
Since the milliequivalents of `KMnO4` and `Na2S2O3` are equal at the point of reaction:
\[ \text{Milliequivalents of } KMnO4 = \text{Milliequivalents of } Na2S2O3 \]
Substituting the expressions we have:
\[ \text{Molarity of } KMnO4 \times n \times 0.1 = 0.1 \times 8 \]

### Step 6: Solve for Molarity of `KMnO4`
Substituting n = 1 into the equation:
\[ \text{Molarity of } KMnO4 \times 1 \times 0.1 = 0.8 \]
\[ \text{Molarity of } KMnO4 = \frac{0.8}{0.1} = 0.8 \, \text{M} \]

### Final Answer
The molarity of the `KMnO4` solution in basic medium is **0.8 M**.

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