Numford
Oxidation number

Fe in K₄[Fe(CN)₆]

Fe is +2 in potassium ferrocyanide.

Oxidation number

Type a formula or an ion: K2Cr2O7, Cr2O7 2-, MnO4-, NH4+ or K4[Fe(CN)6]. Put a known ion in brackets when two elements are unknown. Pick an element to solve for it.

Fe+2

  1. CN⁻ is a known ion with charge −1; there are 6 of them.
  2. K is an alkali metal: +1 in its compounds.
  3. The oxidation numbers add up to the charge, 0: 4(+1) + x + 6(−1) = 0.
  4. x = +2.
Rule steps

How to find it

  1. CN⁻ is a known ion with charge −1; there are 6 of them.
  2. K is an alkali metal: +1 in its compounds.
  3. The oxidation numbers add up to the charge, 0: 4(+1) + x + 6(−1) = 0.
  4. x = +2.
Every atom

All the oxidation numbers in K₄[Fe(CN)₆]

  • K +14 atoms, alkali metal
  • Fe +21 atom, sum rule
  • C +26 atoms, known ion (in CN)
  • N −36 atoms, known ion (in CN)
Questions

Fe in K₄[Fe(CN)₆]: quick answers

What is the oxidation number of Fe in K₄[Fe(CN)₆]?

Fe in K₄[Fe(CN)₆] (potassium ferrocyanide) is +2.

How do you find the oxidation number of Fe in K₄[Fe(CN)₆]?

CN⁻ is a known ion with charge −1; there are 6 of them. K is an alkali metal: +1 in its compounds. The oxidation numbers add up to the charge, 0: 4(+1) + x + 6(−1) = 0. x = +2.

What are the oxidation numbers of the other atoms in K₄[Fe(CN)₆]?

K +1, C +2, N −3. Together with Fe at +2 they add up to the charge of the compound, 0.

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