A brown ring is formed in the ring test for `NO_(3)^(-)` ion. It is due to the formation of

Options

A. `[Fe(H_(2)O)_(5)(NO)]^(2+)`
B. `FeSO_(4)*NO_(2)`
C. `[Fe(H_(2)O)_(4)(NO_(2))]^(2+)`
D. `FeSO_(4)*HNO_(3)`

Answer

A

Explanation

When freshly prepared solution of `FeSO_(4)` is added in a solution containing `NO_(3)^(-)` ion, it leads to formation of a brown coloured complex. This is known as brown ring test of nitrate.
`NO_(3)^(-)+3Fe^(2+)+4H^(+)toNO+3Fe^(3+)+2H_(2)O`
`[Fe(H_(2)O)_(6)]^(2+)+NOtounderset("Brown ring")([Fe(H_(2)O)_(5)(NO)]^(2+)+H_(2)O)`