`As_(2)S_(3)` is soluble in`(NH_(4))_(2)S_(2)` (yellow ammonium sulphide) due to the formation of (a) _____.

Answer

To solve the question, we need to identify the product formed when arsenic trisulfide (As₂S₃) reacts with yellow ammonium sulfide ((NH₄)₂S₂). The reaction leads to the formation of a soluble complex.

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactants in this case are arsenic trisulfide (As₂S₃) and yellow ammonium sulfide ((NH₄)₂S₂).

2. **Write the Reaction**: When arsenic trisulfide reacts with ammonium sulfide, the following reaction occurs:
\[ \text{As}_2\text{S}_3 + 3\text{(NH}_4)_2\text{S}_2 \rightarrow 2\text{(NH}_4)_3\text{AsS}_4 \]
This shows that arsenic trisulfide reacts with ammonium sulfide to form a complex.

3. **Identify the Product**: The product formed from this reaction is ammonium thioarsenate, represented as:
\[ \text{(NH}_4)_3\text{AsS}_4 \]
This complex is responsible for the solubility of arsenic trisulfide in yellow ammonium sulfide.

4. **Conclusion**: Therefore, arsenic trisulfide (As₂S₃) is soluble in yellow ammonium sulfide due to the formation of the complex (NH₄)₃AsS₄.

### Final Answer:
As₂S₃ is soluble in (NH₄)₂S₂ due to the formation of (NH₄)₃AsS₄.

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