`CS_(2)` layer gives a test for

Options

A. `Cl^(-)` only
B. `Br^(-)` and `I^(-)`
C. `Br^(-)` only
D. `I^(-)` only

Explanation

To solve the question "CS₂ layer gives a test for", we need to identify what ions can be detected using the CS₂ (carbon disulfide) layer test, which is also known as the Lassaigne's test. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Purpose of the CS₂ Layer Test
The CS₂ layer test is primarily used to identify the presence of halide ions, specifically bromide (Br⁻) and iodide (I⁻) ions in a solution.

**Hint:** Remember that CS₂ is used in tests for specific ions, particularly halides.

### Step 2: Prepare the Test Solution
To perform the test, we mix the sample solution with dilute nitric acid (HNO₃) and chlorine water (Cl₂ in water). This mixture helps to oxidize the halide ions.

**Hint:** The presence of an oxidizing agent (like chlorine) is crucial for the test to work.

### Step 3: Reaction Mechanism
When the sample containing bromide or iodide ions is added to the mixture, chlorine will oxidize these ions:
- Bromide ions (Br⁻) are oxidized to bromine (Br₂).
- Iodide ions (I⁻) are oxidized to iodine (I₂).

**Hint:** Focus on the oxidation reactions that convert halide ions to their elemental forms.

### Step 4: Observe the Color Change
The products of the oxidation (Br₂ and I₂) are soluble in the CS₂ layer:
- If bromine is present, the CS₂ layer will turn orange.
- If iodine is present, the CS₂ layer will turn violet.

**Hint:** The color change in the organic layer indicates the presence of specific ions.

### Step 5: Conclusion
Since the CS₂ layer test specifically detects the presence of bromide and iodide ions, we can conclude that the CS₂ layer gives a test for bromide and iodide ions.

**Hint:** Remember that chloride ions do not produce a color change in this test, which helps in distinguishing them from bromide and iodide.

### Final Answer
The CS₂ layer gives a test for bromide (Br⁻) and iodide (I⁻) ions.