Assertion :- A sol of `As_(2)S_(3)` prepared by the action of `H_(2)S` on `As_(2)O_(3)` is negatively charge.
Reason :- Due to adsorption of `S^(-2)` ion on surface of `As_(2)S_(3)` sol.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are False.

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that a sol of \( \text{As}_2\text{S}_3 \) (arsenic sulfide) prepared by the action of \( \text{H}_2\text{S} \) on \( \text{As}_2\text{O}_3 \) is negatively charged.

### Step 2: Understand the Reason
The reason given is that this negative charge is due to the adsorption of \( \text{S}^{2-} \) ions on the surface of the \( \text{As}_2\text{S}_3 \) sol.

### Step 3: Analyze the Formation of the Sol
When \( \text{H}_2\text{S} \) reacts with \( \text{As}_2\text{O}_3 \), it leads to the formation of \( \text{As}_2\text{S}_3 \) and releases \( \text{S}^{2-} \) ions into the solution.

### Step 4: Understand Charge Development
In colloidal systems, the charge of the sol can be determined by the ions that preferentially adsorb onto the surface of the particles. In this case, \( \text{S}^{2-} \) ions are negatively charged and preferentially adsorb onto the surface of the \( \text{As}_2\text{S}_3 \) particles.

### Step 5: Conclusion
Since the \( \text{S}^{2-} \) ions are adsorbed onto the surface of the \( \text{As}_2\text{S}_3 \) particles, this results in the overall sol being negatively charged. Therefore, both the assertion and the reason are correct, and the reason correctly explains the assertion.

### Final Answer
Both the assertion and the reason are correct, and the reason is the correct explanation of the assertion.