Question

Which of the following combines with $F{e}^{2+}$ ions to form a brown complex?

• A. $N_{2}O$
• B. $NO$
• C. $N_2{O}_3$
• D. $N_2{O}_5$

Answer 1

Answer: (B)

Nitric oxide (NO) may contain impurities of $N{O}_2$ and $N{O}_2$. It is purified by absorbing it in ferrous sulphate $\left(F{e}^{2+}\right)$ solution, the dark brown nitro so ferrous sulphate is obtained, on heating it pure nitric oxide is liberated.
$\left[Fe{\left(H_{2}O\right)}_6\right]S{O}_4+\underset{\text{ impure gas }}{\mathrm{NO}}\stackrel{-H_{2}O}{\to }\left[Fe{\left(H_{2}O\right)}_{5}NO\right]$
$S{O}_4\stackrel{\text{ heat }}{\to }FeS{O}_4+\underset{\text{ pure gas }}{\mathrm{NO}}+5H_{2}O$