Assertion (A): Addtion of `NH_(4)OH` to an aqueous solution of `BaCl_(2)` in the presence of excess of `NH_(4)Cl` precipitates `Ba(OH)_(2)`.
Reason (R ): `Ba(OH)_(2)` is insoluble in water.

Options

A. If both `(A)` and `(R )` are correct 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 incrrect, but `(R )` is correct.

Explanation

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step 1: Analyze the Assertion (A)
The assertion states that the addition of \( NH_4OH \) to an aqueous solution of \( BaCl_2 \) in the presence of excess \( NH_4Cl \) precipitates \( Ba(OH)_2 \).

- When \( NH_4OH \) (ammonium hydroxide) is added to \( BaCl_2 \) (barium chloride), it is expected to produce \( Ba(OH)_2 \) (barium hydroxide) and \( NH_4Cl \) (ammonium chloride).
- However, the presence of excess \( NH_4Cl \) suppresses the dissociation of \( NH_4OH \) into \( NH_4^+ \) and \( OH^- \) ions. This means that the concentration of \( OH^- \) ions is significantly reduced.
- Since \( Ba(OH)_2 \) requires \( OH^- \) ions to precipitate, the low concentration of \( OH^- \) ions means that \( Ba(OH)_2 \) will not precipitate.

**Conclusion for Assertion (A)**: The assertion is **incorrect**.

### Step 2: Analyze the Reason (R)
The reason states that \( Ba(OH)_2 \) is insoluble in water.

- \( Ba(OH)_2 \) is indeed considered to be insoluble in water, although it has some solubility. However, for practical purposes in this context, we can consider it as insoluble.
- This statement is **correct**.

### Final Conclusion
- The assertion (A) is incorrect because \( Ba(OH)_2 \) does not precipitate in the presence of excess \( NH_4Cl \).
- The reason (R) is correct because \( Ba(OH)_2 \) is indeed insoluble in water.

Thus, the correct answer is that the assertion is incorrect, but the reason is correct.

### Answer:
Assertion (A) is incorrect, and Reason (R) is correct.

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