Question

Oxidation number of $Fe$ in $N{a}_2\left[Fe\right(CN{)}_5\left(NO\right)].2H_{2}O$ is____________.

• A. $-2$
• B. $+1$
• C. $+3$
• D. $+5$

Answer 1

Answer: (C)

$+3$

Let $x$ be the oxidation number of $Fe$.
The oxidation numbers of $N{a}^{+},C{N}^{-}$ ion and $NO$ group are $+1,-1$ and $0$ respectively. The sum of the oxidation numbers is zero as the compound is neutral.
Hence, $2(+1)+x+5(-1)+0=0$ or, $x=+3$.
The oxidation state of iron in $N{a}_2\left[Fe\right(CN{)}_5\left(NO\right)].2H_{2}O$ is $+3$.