The brown ring test is performed for the qualitative detection of

Options

A. Bromides
B. Iodides
C. Nitrates
D. Nitrite

Answer

### Step-by-Step Solution:

1. **Understanding the Brown Ring Test**: The brown ring test is a qualitative analysis method used specifically for the detection of nitrate ions (NO3⁻) in a solution.

2. **Preparation of the Test**: To perform the brown ring test, you need to prepare a solution that contains nitrate ions. This can be done by dissolving a nitrate salt in water.

3. **Adding Iron(II) Sulfate**: Once you have the nitrate solution, you will add Iron(II) sulfate (FeSO4) to the solution. This is crucial as the iron(II) ions (Fe²⁺) will react with the nitrate ions.

4. **Adding Concentrated Sulfuric Acid**: After adding Iron(II) sulfate, you must carefully add concentrated sulfuric acid (H2SO4) to the solution. It is important to add the acid slowly and without stirring to ensure that a distinct layer of sulfuric acid forms below the aqueous solution.

5. **Formation of the Brown Ring**: If nitrate ions are present in the solution, a brown ring will form at the interface of the two layers (the aqueous layer and the sulfuric acid layer). This brown ring is due to the formation of a complex known as [Fe(H2O)5NO]²⁺.

6. **Chemical Reaction**: The chemical reaction that occurs can be summarized as follows:
- Nitrate ions (NO3⁻) react with Iron(II) ions (Fe²⁺) in the presence of hydrogen ions (H⁺) from sulfuric acid to form nitrogen monoxide (NO) and Iron(III) ions (Fe³⁺).
- The resulting Iron(III) ions then form a complex with water and nitrogen monoxide, leading to the formation of the brown ring.

7. **Conclusion**: The brown ring test is specifically used for the qualitative detection of nitrates. Therefore, the correct answer to the question is that the brown ring test is performed for the qualitative detection of nitrates.