A : When `Cu_(2)S` is converted into `Cu^(++)" & " SO_(2)`, then equivalent weight of `Cu_(2)S` will be M/8 (M = Mol. wt. of `Cu_(2)S`)
R : `Cu^(+)` is converted `Cu^(++)`, during this one electrons is lost.

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 determine the equivalent weight of \( \text{Cu}_2\text{S} \) when it is converted into \( \text{Cu}^{2+} \) and \( \text{SO}_2 \), we need to analyze the changes in oxidation states and calculate the valency factor.

### Step-by-Step Solution:

1. **Identify the Oxidation States**:
- In \( \text{Cu}_2\text{S} \), copper (Cu) is in the +1 oxidation state and sulfur (S) is in the -2 oxidation state.
- When \( \text{Cu}_2\text{S} \) is converted to \( \text{Cu}^{2+} \) and \( \text{SO}_2 \), the oxidation states change as follows:
- Copper changes from +1 to +2 (each Cu atom).
- Sulfur changes from -2 in \( \text{Cu}_2\text{S} \) to +4 in \( \text{SO}_2 \).

2. **Calculate the Change in Oxidation States**:
- For Copper:
- Each Cu changes from +1 to +2, which is an increase of 1 for each of the 2 Cu atoms: \( 2 \times (2 - 1) = 2 \).
- For Sulfur:
- Sulfur changes from -2 to +4, which is an increase of 6: \( 4 - (-2) = 6 \).

3. **Determine the Total Change in Electrons**:
- Total change in electrons = Change for Cu + Change for S = \( 2 + 6 = 8 \).

4. **Calculate the Valency Factor**:
- The valency factor (n) is the total change in electrons, which we found to be 8.

5. **Calculate the Equivalent Weight**:
- The equivalent weight of a substance is given by the formula:
\[ \text{Equivalent Weight} = \frac{\text{Molecular Weight}}{\text{Valency Factor}} \]
- Therefore, for \( \text{Cu}_2\text{S} \):
\[ \text{Equivalent Weight} = \frac{M}{8} \quad \text{(where M is the molar mass of } \text{Cu}_2\text{S)} \]

6. **Conclusion**:
- The assertion that the equivalent weight of \( \text{Cu}_2\text{S} \) will be \( \frac{M}{8} \) is correct.
- The reasoning that \( \text{Cu}^+ \) is converted to \( \text{Cu}^{2+} \) by losing one electron is also correct.

### Final Answer:
- Both the assertion (A) and reasoning (R) are correct.