Oxidation state of Fe in Na4[Fe(CN)5(NOS)]:
Charge of CN =−1
Charge of NOS=−1
Suppose oxidation state of Fe=x
4+x−5−1=0⇒x=+2
Oxidation state of FeinNa4[FeO4]:
4+x−8=0⇒x=+4
Oxidation state of Fein[Fe2(CO)9] =0 because carbonyl is neutral ligand.
The oxidation states of iron in these compounds will be
A=+2B=+4C=0The sum of oxidation states will be =6.