JEE Main levelSingle correct optionDifficulty 2 of 3qa207
In the brown ring test the complex [Fe(HX2O)X5NO]X2+ is formulated with NO as NOX+. The oxidation state of iron is
A+3
B+2
C+1
D0
Answer: C
The charge on the complex is +2. With five neutral HX2O and NOX+, x+0+1=+2, so x=+1. This is why the brown ring complex is described as an iron(I) nitrosyl.