A : Equivalent weight of `KMnO_(4)` in acidic medium is `M/5`.
R : In acidic medium 1 mol of `MnO_(4)""^(-)` gains 5 electron.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4).

Answer

To solve the question regarding the assertion and reason statements about the equivalent weight of KMnO4 in acidic medium, we will break down the concepts step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the equivalent weight of KMnO4 in acidic medium is \( \frac{M}{5} \), where \( M \) is the molar mass of KMnO4.

2. **Understanding the Reason**:
- The reason states that in acidic medium, 1 mole of \( \text{MnO}_4^- \) gains 5 electrons.

3. **Analyzing the Reaction**:
- In acidic medium, the reduction reaction of \( \text{MnO}_4^- \) can be represented as:
\[ \text{MnO}_4^- + 8 \text{H}^+ + 5 \text{e}^- \rightarrow \text{Mn}^{2+} + 4 \text{H}_2\text{O} \]
- Here, \( \text{MnO}_4^- \) is reduced to \( \text{Mn}^{2+} \).

4. **Calculating Oxidation States**:
- The oxidation state of manganese in \( \text{MnO}_4^- \) is +7 (calculated as follows):
\[ x + 4(-2) = -1 \implies x - 8 = -1 \implies x = +7 \]
- In \( \text{Mn}^{2+} \), the oxidation state is +2.

5. **Determining the Change in Oxidation State**:
- The change in oxidation state for manganese is:
\[ +7 \text{ (in } \text{MnO}_4^-\text{)} \rightarrow +2 \text{ (in } \text{Mn}^{2+}\text{)} \]
- This indicates that manganese gains 5 electrons during the reduction.

6. **Finding the Equivalent Weight**:
- The equivalent weight is defined as:
\[ \text{Equivalent Weight} = \frac{\text{Molar Mass}}{n} \]
- Here, \( n \) is the number of electrons gained or lost, which is 5 in this case.
- Therefore, the equivalent weight of KMnO4 in acidic medium is:
\[ \text{Equivalent Weight} = \frac{M}{5} \]

7. **Conclusion**:
- Both the assertion and the reason are true. The reason correctly explains the assertion.

### Final Answer:
Both the assertion and reason are true, and the reason is the correct explanation of the assertion.