QJEEM20Ch557d: JEE Main 2020 Chemistry - Class 12 JEEM20Ch557d Solution: The oxidation states of iron atoms in compounds (A), (B) and…

Na₄[Fe(CN)₅(NOS)]

Let the O.S. of Fe be x

OS of CN = –1
OS of NOS = –1

$\therefore$ (+1)4 + x + (–1)5 + (–1)1 = 0

$\Rightarrow$ x = +2

Na₄[FeO₄]

Let O.S. of Fe be y

(+1)4 + y + (–2)4 = 0

$\Rightarrow$ y = +4

[Fe₂(CO)₉]

Let O.S. of Fe be z

2z + 0 × 9 = 0

$\Rightarrow$ z = 0

so (x + y + z) = +2 + 4 + 0 = 6