(a) Explain with the help of a balanced equation, the brown ring test for nitric acid.
(b) Why is freshly pepared ferrous sulphate solution used for testing the nitrate radical in the brown ring test ?
(a) Explain with the help of a balanced equation, the brown ring test for nitric acid.
(b) Why is freshly pepared ferrous sulphate solution used for testing the nitrate radical in the brown ring test ?
(a) Brown ring test
Procedure:
(i) Add freshly prepared saturated solution of iron (II)sulphate to the aq. solution of nitric acid.
(ii) Now add conc. Sulphuric acid carefully from the sides of the test tube, so that it
should not fall drop wise in the test tube.
(iii) Cool the test tube in water.
(iv) A brown ring appears at the junction of the two liquids.
6FeSO4 + 2HNO3 + 3H2SO4 ⇒ 3Fe2(SO4)3 + 2NO + 4H2O
Fe(H2O)6]SO4 + NO ⇒ [Fe(H2O)5(NO)]SO4+ H2O
(b) A freshly prepared ferrous sulphate solution is used because on exposure to the
atmosphere, it is oxidized to ferric sulphate which will not give the brown ring.
(a) Brown ring test
Procedure:
(i) Add freshly prepared saturated solution of iron (II)sulphate to the aq. solution of nitric acid.
(ii) Now add conc. Sulphuric acid carefully from the sides of the test tube, so that it
should not fall drop wise in the test tube.
(iii) Cool the test tube in water.
(iv) A brown ring appears at the junction of the two liquids.
6FeSO4 + 2HNO3 + 3H2SO4 ⇒ 3Fe2(SO4)3 + 2NO + 4H2O
Fe(H2O)6]SO4 + NO ⇒ [Fe(H2O)5(NO)]SO4+ H2O
(b) A freshly prepared ferrous sulphate solution is used because on exposure to the
atmosphere, it is oxidized to ferric sulphate which will not give the brown ring.
