Ring test for mirates conformed by acidifying prepared `FeSO_(4)` soin a brown ring is formed that to the formation of `[Fe(H_(2)O)_(3)NO[SO_(4)` This rest should not be performed for nitrate ion in presence of

Options

A. `NO_(2)^(Theta)`
B. `Bi^(Theta)`
C. `I^(Theta)`
D. All

Answer

### Step-by-Step Solution:

1. **Understanding the Ring Test for Nitrates**:
The ring test is a qualitative analysis method used to detect the presence of nitrate ions (NO₃⁻) in a solution. This test involves the use of ferrous sulfate (FeSO₄) and concentrated sulfuric acid (H₂SO₄).

2. **Preparation of the Test Solution**:
To perform the ring test, prepare a solution containing ferrous sulfate (FeSO₄) and add concentrated sulfuric acid (H₂SO₄) to it. The ferrous ions (Fe²⁺) in the solution will react with the nitrate ions.

3. **Reaction Mechanism**:
When the nitrate ion reacts with ferrous sulfate in the presence of sulfuric acid, the following redox reaction occurs:
- The nitrate ion (NO₃⁻) oxidizes the ferrous ion (Fe²⁺) to ferric ion (Fe³⁺), while itself being reduced to nitric oxide (NO).
- The overall reaction can be represented as:
\[ 3 \text{Fe}^{2+} + 2 \text{NO}_3^{-} + 4 \text{H}^{+} \rightarrow 3 \text{Fe}^{3+} + 2 \text{NO} + 2 \text{H}_2\text{O} \]

4. **Formation of the Brown Ring**:
The nitric oxide (NO) produced in the reaction then forms a complex with the ferric ion and water, resulting in the formation of a brown ring at the interface of the two liquids:
\[ \text{Fe(H}_2\text{O)}_5\text{NO}^{2+} \]
This brown ring indicates the presence of nitrate ions in the solution.

5. **Interference from Nitrite Ions**:
The ring test should not be performed in the presence of nitrite ions (NO₂⁻). This is because nitrites can interfere with the detection of nitrates, leading to false results.

6. **Removing Nitrite Ions**:
If both nitrate and nitrite ions are present, nitrite can be removed by treating the solution with sodium carbonate (Na₂CO₃) and then boiling it with urea (NH₂CONH₂). This process decomposes the nitrite ions, allowing for the accurate detection of nitrate ions.

7. **Conclusion**:
Therefore, the ring test for nitrate ions should not be performed in the presence of nitrite ions, as they interfere with the test results.