Assertion: `Zn(OH)_(2)` dissolves in an excess of NaOH solution as well as `NH_(4)OH` solution.
Reason: `Zn(OH)_(2)` forms the soluble zincate salts with these alkalies.

Options

A. If assertion is true but the reason is false
B. If assertion is false but reason is true
C. If both assertion and reason are true and reason is the correct explanation of assertion
D. If oth assertion and reason are true but reason is not the correct explanation of assertion

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that zinc hydroxide, \( Zn(OH)_2 \), dissolves in excess sodium hydroxide (NaOH) and ammonium hydroxide (NH4OH).

2. **Dissolution in NaOH**: When \( Zn(OH)_2 \) is added to an excess of NaOH, it reacts to form sodium zincate, \( Na_2ZnO_2 \), and water. The reaction can be represented as:
\[ Zn(OH)_2 + 2NaOH \rightarrow Na_2ZnO_2 + 2H_2O \]
This indicates that \( Zn(OH)_2 \) is soluble in NaOH.

3. **Dissolution in NH4OH**: Similarly, when \( Zn(OH)_2 \) is treated with NH4OH, it forms tetraamine zinc hydroxide, which is also soluble. The reaction can be represented as:
\[ Zn(OH)_2 + 4NH_4OH \rightarrow [Zn(NH_3)_4](OH)_2 + 4H_2O \]
This shows that \( Zn(OH)_2 \) dissolves in NH4OH as well.

4. **Conclusion on Assertion**: Since \( Zn(OH)_2 \) does dissolve in both NaOH and NH4OH, the assertion is **true**.

5. **Understanding the Reason**: The reason states that \( Zn(OH)_2 \) forms soluble zincate salts with these alkalies. However, while it does form sodium zincate with NaOH, the statement about forming zincate salts with NH4OH is misleading because the product is not a typical zincate salt but a complex ion.

6. **Conclusion on Reason**: The reason provided is **false** because it incorrectly describes the nature of the product formed with NH4OH.

7. **Final Evaluation**: Based on the analysis, the assertion is true, but the reason is false. Therefore, the correct answer is: **Assertion is true, but reason is false**.