Q. 154.5( 4 Votes )
A brown ring is f A. [Fe(H2O)5 (NO)]2+
When freshly prepared solution of FeSO4 is added in the solution containing NO3 ion. It leads to the formation of brown coloured complex. This is known as brown colour test of nitrate.
+ 3Fe2+ + 4H+ NO + 3Fe3+ + 2H2O
[Fe(H2O6)]2+ + NO [Fe(H2O)5 (NO)]2+ + H2O
Hence the correct option is (i).
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