Assertion (A): `Sb^(3+)` is not precipitated as sulphide when `H_(2)S (g)` is passed in alkaline solution.
Reason (R) : `[S^(2-)]` ion in basic medium is inadequate for precipitation.

Options

A. If both (A) and (R) are correc, and (R) is the correct explanation of (A).
B. If both (A) and (R) are correct but (R) is not the correct explanation of (A).
C. If (A) is correct, but (R) is incorrect.
D. If (A) is incorrect, but (R) is correct.

Explanation

To solve the assertion and reasoning question regarding the precipitation of `Sb^(3+)` as sulfide in alkaline solution when `H2S (g)` is passed, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that `Sb^(3+)` is not precipitated as sulfide when `H2S (g)` is passed in alkaline solution.
- This is true because `Sb^(3+)` typically precipitates as sulfide in acidic conditions, not in alkaline conditions.

2. **Understanding the Reason (R)**:
- The reason provided is that `[S^(2-)]` ions in basic medium are inadequate for precipitation.
- This statement is misleading. In alkaline conditions, the concentration of sulfide ions `[S^(2-)]` is actually sufficient to precipitate certain metal ions, particularly those from groups that can form sulfides.

3. **Analyzing the Conditions**:
- In acidic medium, the concentration of sulfide ions is lower, which allows for the precipitation of `Sb^(3+)` as sulfide.
- In contrast, in alkaline medium, the higher concentration of sulfide ions may lead to the precipitation of other metal ions, but not `Sb^(3+)`.

4. **Conclusion**:
- The assertion is correct: `Sb^(3+)` does not precipitate as sulfide in alkaline conditions.
- The reason is incorrect: `[S^(2-)]` ions in basic medium are not inadequate; they are present in sufficient amounts.

5. **Final Answer**:
- Therefore, the correct conclusion is that Assertion (A) is true, and Reason (R) is false. The answer choice that reflects this is option C (A is correct, R is incorrect).