Which of the following is formed when `As_(2)S_(3)` is warmed with `NH_(4)OH and H_(2)O_(2)` ?

Options

A. `As(OH)_(3)`
B. `AsO_(4)^(3-)`
C. `AsO_(3)^(2-)`
D. `[As(NH_(3))_(6)]^(5+)`

Answer

To determine which compound is formed when As₂S₃ is warmed with NH₄OH and H₂O₂, we can follow these steps:

### Step 1: Identify the Reactants
The reactants in this reaction are arsenic trisulfide (As₂S₃), ammonium hydroxide (NH₄OH), and hydrogen peroxide (H₂O₂).

**Hint:** Recognize the chemical formulas of the reactants and their common uses in qualitative analysis.

### Step 2: Understand the Reaction
When As₂S₃ reacts with NH₄OH and H₂O₂, it undergoes a redox reaction. Hydrogen peroxide acts as an oxidizing agent, while ammonium hydroxide provides a basic medium.

**Hint:** Consider how oxidation and reduction processes occur in reactions involving H₂O₂.

### Step 3: Write the Reaction Equation
The reaction can be represented as follows:
\[ \text{As}_2\text{S}_3 + \text{NH}_4\text{OH} + \text{H}_2\text{O}_2 \rightarrow \text{NH}_4\text{3AsO}_4 + \text{NH}_4\text{2SO}_4 + \text{H}_2\text{O} \]
In this reaction, arsenic sulfide is converted into ammonium arsenate and ammonium sulfate.

**Hint:** Pay attention to the products formed and their respective charges.

### Step 4: Determine the Charge of the Arsenate Ion
From the reaction, we can see that the ammonium arsenate formed is represented as \( \text{NH}_4\text{3AsO}_4 \). The arsenate ion (AsO₄) has a charge of -3.

**Hint:** Remember that the overall charge of the compound must balance with the positive charges from ammonium ions.

### Step 5: Identify the Final Product
The final product of the reaction is the arsenate ion, which is \( \text{AsO}_4^{3-} \).

**Hint:** Look for the specific ion that corresponds to the product formed in the reaction.

### Conclusion
When As₂S₃ is warmed with NH₄OH and H₂O₂, the compound formed is \( \text{AsO}_4^{3-} \).

**Final Answer:** The correct option is \( \text{AsO}_4^{3-} \).

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