Question

A brown ring is formed in the ring test for \[\ce{NO3^{-}}\] ion. It is due to the formation of ______.

विकल्प

• \[\ce{[Fe(H2O)5 (NO)]^{2+}}\]

• \[\ce{FeSO4.NO2}\]

• \[\ce{[Fe(H2O)4(NO)2]^{2+}}\]

• \[\ce{FeSO4.HNO3}\]

Answer 1

A brown ring is formed in the ring test for \[\ce{NO_{3}^{-}}\] ion. It is due to the formation of \[\ce{[Fe(H2O)5 (NO)]^{2+}}\].

Explanation:

When freshly prepared solution of \[\ce{FeSO4}\] is added in a solution containing \[\ce{NO3}\] ion, it leads to formation of a brown coloured complex. This is known as brown ring test of nitrate.

\[\ce{NO3^{-} + 3Fe^{2+} + 4H^{+} -> NO + 3Fe^{3+} + 2H2O}\]

\[\ce{[Fe(H2O)6]^{2+} + NO -> \underset{Brown ring}{[Fe(H2O)5(NO)]^{2+} + H2O}}\]

Hence, 2 moles of ammonia will produce 2 moles of NO.