The brown ring complex compound is formulated as `[Fe(H_(2)O)_(5)NO]SO_(4)`. The oxidation state of `Fe` is

Options

A. 1
B. 0
C. 2
D. 3

Answer

A

Explanation

NO readily forms coordination complexes with transition metal ions. These complexes are called nitrosyls. `Fe^(2+)` and NO form the complex `[Fe(H_(2)O)_(5)NO]^(2+)`, which is responsible for the colour in the brown-ring test for nitrates. The colour is due to charge transfer. This complex formally contains Fe(+1) and `NO^(+)`. Its magnetic moment is approximately 3.9 BM, confirming the presence of three unpaired electrons.