The brown ring complex compound is formulated as [Fe (H2O)5 NO]SO4. The oxidation state of iron is (a) +1 (b) +2 (c) +3 (d) +6

Answer: The Correct option is (a) +1

A chemical test termed a nitrate test is used to identify the presence of nitrate ions in any solution. In the presence of nitrate, the liquids in the test tube create a brown ring. As a result, it’s known as the brown ring test.

The oxidation number of iron in the aforementioned compound may be calculated as follows: 

[Fe (NO) (H2O)5]SO4 in water, dissociate to produce [Fe (NO) (H2O)5]2+ ions and SO42- ions.

Charge on NO is +1 (NO+)

H2O is a neutral ligand.

The oxidation state of iron (Fe) can now be calculated as follows:

⇒ X + (+1) + 5(0) = +2

⇒ X = +1