Answer the following questions pertaining to the brown ring test for nitric acid:

1. Name the chemical constituent of the brown ring 'Y'.
2. Which of the two solutions – iron [II] sulphate or conc. sulphuric acid, do 'X' and 'Z' represent.
3. State why the unstable brown ring decomposes completely on disturbing the test tube.
4. Give a reason why the brown ring does not settle down at the bottom of the test tube.
5. Name the gas evolved when acidified iron [II] sulphate reacts with dilute nitric acid in the brown ring test.

1. Nitroso Iron (II) Sulphate (FeSO₄.NO).
2. X is Iron (II) Sulphate (FeSO₄) and Z is conc. Sulphuric Acid (H₂SO₄).
3. When the test tube is shaken the conc. sulphuric acid may further mix with water and the heat evolved assists in decomposing the unstable brown ring. Hence, unstable brown ring of nitroso ferrous sulphate decomposes completely on disturbing.
4. In the brown ring test the conc. sulphuric acid being heavier settles down and the iron [II] sulphate layer remains above it resulting in formation of the brown ring at the junction.
5. Nitric oxide
   6FeSO₄ + 3H₂SO₄ + 2HNO₃ ⟶ 3Fe₂(SO₄)₃ + 4H₂O + 2NO