Question

Difficulty: EasyTransition Metals: General Properties, Catalytic Behavior, and Complex Ions

What is the oxidation state of the central iron atom in the hexacyanoferrate(III) complex ion, [Fe(CN)6]3[Fe(CN)_6]^{3-}?

  1. +3+3Answer
  2. B
    +2+2
  3. C
    +6+6
  4. D
    3-3

Answer

The oxidation state of the central iron atom in [Fe(CN)6]3[Fe(CN)_6]^{3-} is +3+3.
In the complex ion [Fe(CN)6]3[Fe(CN)_6]^{3-}, six anionic cyanide ligands (CNCN^-), each with a 1-1 charge, bond to the central iron atom. The sum of the oxidation state of iron (xx) and the total ligand charge (6×1=66 \times -1 = -6) equals the overall charge of the complex ion (3-3). Solving x6=3x - 6 = -3 gives x=+3x = +3.

Step-by-Step Solution

1
Identify the charge of the ligands and the net charge of the complex ion.
Each cyanide ligand (CNCN^-) carries a 1-1 charge. The overall complex ion has a net charge of 3-3.
Ligand charges must sum with the central metal oxidation state to equal the overall ion charge.
2
Set up an algebraic equation for the oxidation state of iron (xx).
x+6(1)=3    x6=3    x=+3x + 6(-1) = -3 \implies x - 6 = -3 \implies x = +3.
Solving the linear algebraic equation yields the precise oxidation state of the central atom.

Key Concept

Determination of central metal oxidation state in complex ions
Estimated Time:45s
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