Question

The complex $\left[ Fe \left( H _2 O \right)_5 NO \right]^{2+}$ is formed in the brown ring test nitrates when freshly prepared $FeSO _4$ solution is added to aqueous solution of $NO _3^{-}$followed by addition of conc. $H _2 SO _4$ Select correct statement about this complex

• A. Colour change is due to charge transfer
• B. It has iron in $+1$ oxidate state and nitrosyl as $NO ^{+}$
• C. It has magnetic moment of $3.87 BM$ confirming three unpaired electrons in $Fe$
• D. All the above are correct statements

Answer 1

Answer: (D)

$Fe ^{2+}$ changes to brown-coloured ring complex
(b) $ NO \rightarrow NO ^{+}+e^{-}$
$Fe ^{2+}+e^{-} \rightarrow Fe ^{+}$

Magnetic moment $=\sqrt{N(N+2)}=\sqrt{15}=$ $3.87$ BM
Thus, (a), (b) and (c) are true