In the ring test of NO₃^– ion, Fe²⁺ ion reduces nitrate ion to nitric oxide, which combines with Fe²⁺ (aq.) ions to form brown complex. Write reactions involved in the formation of a brown ring.

Ring test is used to detect the presence of nitrate ions (NO₃^-) in chemistry qualitative analysis. The required chemical reactions involved for the Ring test' is:

i) NO₃^- + conc.H₂SO₄→ HSO₄^- + HNO₃

ii) 2HNO₃→ 2NO + H₂O + 3O

iii) 6FeSO₄ + 3O+ 3H₂SO ₄→ 3Fe₂(SO₄)₃ + 3H₂O

iv) 6FeSO₄ + 2HNO₃ + 3H₂SO₄ → 3Fe₂(SO₄)₃ + 2NO +4H₂O

v) FeSO₄ + NO + 5H₂O →

Brown ring is formed at the junction of the layers of the solution and sulphuric acid is obtained, which confirms the presence of nitrate ions in the solution.