In the ring test of NO3 ion, Fe2+ ion reduces nitrate ion to nitric oxide, which

combines with Fe2+ (aq) ion to form brown complex. Write the reactions involved in the formation of brown ring.


+ 3Fe2+ + 4H+ NO + 3Fe2+ 2H2O


[Fe(H2O)6]SO4 + NO [Fe(H2O)5NO]SO4


Thus the complex formed is brown in colour.


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