Question

Iron is in +2 oxidation state in:

• A. $N{a}_2\left[Fe\right(CN{)}_{5}NO]$
• B. $\left[Fe\right(H_{2}O{)}_{5}NO]S{O}_4$
• C. $K_3\left[Fe\right(CN{)}_6]$
• D. $K_4\left[Fe\right(CN{)}_6]$

Answer 1

Answer: (A), (D)

The correct options are
A $K_4\left[Fe\right(CN{)}_6]$
D $N{a}_2\left[Fe\right(CN{)}_{5}NO]$

Iron is in +2 oxidation state in the compounds of options $A$ and $D$.
In option $B$, $Fe$ is in +1 oxidation state.
In option $C$, iron is in +3 oxidation state.

Let $X$ be the oxidation state of iron.

$\left(A\right)$ $+2+X+5(-1)+1=0$
$X=+2$

$\left(B\right)$ $X+5\left(0\right)+1-2=0$
$X=+1$

$\left(C\right)$ $+3+X+6(-1)=0$
$X=+3$

$\left(D\right)$ $+4+X+6(-1)$
$X=+2$