A : `Al^(+3)` can be used for the cagulation of `As_(2) S_(3)` sol .
R : `Al^(+3)` reacts with `As_(2)S_(3) "to give" Al_(2) S_(3)`

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, mark (1)
B. If both Assertion & Reason are true but reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Resson are false statements , then mark (4)

Answer

To solve the question regarding the coagulation of `As2S3` sol by `Al^(+3)`, we will analyze the statements provided and determine their validity step by step.

### Step 1: Understanding Coagulation
Coagulation is the process where colloidal particles come together to form larger aggregates, which can then settle out of the solution. In this case, we are dealing with a negatively charged sol of `As2S3`.

**Hint:** Coagulation involves the neutralization of charges to allow particles to aggregate.

### Step 2: Charge of `As2S3` Sol
The `As2S3` sol is negatively charged due to the presence of `As2-` ions. This negative charge causes repulsion between the particles, preventing them from coming together.

**Hint:** Identify the charge of the colloidal particles to understand the coagulation process.

### Step 3: Role of `Al^(+3)`
`Al^(+3)` is a positively charged ion. To coagulate the negatively charged `As2S3` sol, a positive charge is needed to neutralize the negative charge of the particles. When `Al^(+3)` is introduced, it can adsorb onto the surface of the `As2S3` particles.

**Hint:** Positive ions are used to neutralize negative charges in colloidal systems.

### Step 4: Adsorption Process
The adsorption of `Al^(+3)` onto the `As2S3` particles neutralizes their negative charge. Once the charge is neutralized, the repulsive forces between the particles diminish, allowing them to come closer and eventually aggregate to form a precipitate.

**Hint:** Adsorption is key in coagulation; it helps neutralize charges.

### Step 5: Evaluating the Reaction
The statement claims that `Al^(+3)` reacts with `As2S3` to form `Al2S3`. However, this is incorrect. Instead of forming a new compound, `Al^(+3)` simply adsorbs onto the `As2S3` particles, facilitating coagulation without forming `Al2S3`.

**Hint:** Distinguish between chemical reactions and physical processes like adsorption.

### Conclusion
- **Statement A** is true: `Al^(+3)` can be used for the coagulation of `As2S3` sol.
- **Statement R** is false: `Al^(+3)` does not react with `As2S3` to form `Al2S3`; it adsorbs onto the particles instead.

### Final Answer
The correct answer is that Statement A is true, and Statement R is false.

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