What is the formula of brown …

A nitrate test is a chemical test used to determine the presence of nitrate ion in solution.

A nitrate test, known as the brown ring test can be performed by adding iron(II) sulfate to the solution, then slowly adding concentrated sulfuric acid and watching for a brown ring on the test tube, which will indicate the presence of the nitrate ion.

The test follows several phases; these have been written as balanced chemical equations:

1: 2 Zn(NO₃)₂ + 2 H₂SO₄ → 2 ZnSO₄ + 4 HNO₃

4 FeSO₄ + 2 H₂SO₄ → 2 Fe₂(SO₄ )₃ + H₂

These two reactions happen simultaneously.

2: 4 HNO₃ → 2 H₂O + 3O₂ + 2 NO

The Nitric Acid decomposes in the intense heat produced by the high concentrate Sulphuric Acid used.

3: 2 Fe₂(SO₄)₃ + 2 H₂ + 4 NO → 4 Fe.NO.SO₄ + 2 H₂SO₄

The Fe.NO.SO₄ forms a brown ring in the middle of the solution produced by the reaction, making it easy to identify the presence of nitrates in the water.