Question

The oxidation number of Fe in K₄[Fe(CN)₆] is ____________.

Options

• +3

• +1

• +2

• 0

Answer 1

The oxidation number of Fe in K₄[Fe(CN)₆] is +2.

Explanation:

The ligand CN​​​​​⁻ has charge of –1. So the overall charge carried by 6 CN​​​​​⁻ ligands is –6. Each potassium ion K⁺ carries a charge of +1. So 4 potassium ions carry an overall charge of +4. This implies that the overall charge on the coordination sphere is –4 to balance the +4 charge of the potassium ions. Let the oxidation number of Fe be x. Then

x + (–6) = –4

x = –4 – (–6)

x = –4 + 6

x = +2

So, the oxidation number of Fe is +2.