The Brown Ring test for nitrate () ions involves the formation of a brown coordination complex at th — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

In the brown ring complex $[Fe(H_2O)_5NO]SO_4$, the $NO$ ligand is an unusual non-innocent ligand that donates an electron to the $Fe^{2+}$ center, reducing the iron to a $+1$ oxidation state while the ligand becomes $NO^+$. Thus, iron has a $3d^7$ configuration with 3 unpaired electrons, making option B conceptually incorrect.