Brown ring test s performed for which ion?

Options

A. `NO_2^-`
B. `NO_3^-`
C. `HO^-`
D. H_2N^-

Answer

**Step-by-Step Solution:**

1. **Understanding the Brown Ring Test:**
The Brown Ring Test is a qualitative analysis test used to detect the presence of certain ions in a solution. Specifically, it is used to identify the nitrate ion (NO3-).

2. **Reagents Required:**
The test involves the use of ferrous sulfate (FeSO4) and concentrated sulfuric acid (H2SO4). When these reagents are mixed with a solution containing nitrate ions, a characteristic brown ring forms.

3. **Reaction Mechanism:**
- When nitrate ions (NO3-) are present in the solution, they react with ferrous ions (Fe2+) in the presence of sulfuric acid.
- The ferrous ions are oxidized to ferric ions (Fe3+), and the nitrate ions are reduced to nitric oxide (NO).

4. **Formation of the Brown Ring:**
- The nitric oxide (NO) produced in the reaction then reacts with the ferric ions (Fe3+) to form a complex known as nitrosyl ferrous complex, which is responsible for the brown color observed in the test.
- The complex formed is [Fe(H2O)5NO]2+, which is also referred to as penta-aqua nitrosyl iron(II).

5. **Conclusion:**
The presence of the brown ring indicates a positive result for the presence of nitrate ions (NO3-) in the solution. Therefore, the brown ring test is specifically performed for the detection of the nitrate ion.

**Final Answer:**
The brown ring test is performed for the nitrate ion (NO3-).

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