Question

What is the correct IUPAC name of \(\text{K}_{3}[\text{Fe(CN)}_{6}]\)?

• A. Potassium hexacyanoferrate(II)
• B. Potassium hexacyanoferrate(III)
• C. Potassium ferricyanide
• D. Potassium ferrocyanide

Hint:

Name the ligands, then the metal with the ending -ate for an anionic complex, and give the oxidation state of iron in Roman numerals.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
In IUPAC naming, the cation is named first, then ligands (alphabetical, with prefixes), then the metal with its oxidation state in brackets. An anionic complex ends in -ate, and iron becomes ferrate.

Step 2: Calculation
The complex ion is \([\text{Fe(CN)}_{6}]^{3-}\) because three \(\text{K}^{+}\) balance it.
Let the oxidation state of Fe be \(x\): \(x + 6(-1) = -3\), so \(x = +3\).
Six cyanide ligands are called hexacyano.

Step 3: Compare the options
Potassium hexacyanoferrate(II) gives the wrong oxidation state. Ferricyanide and ferrocyanide are common names, not IUPAC names. So the answer is potassium hexacyanoferrate(III).

Final Answer:
The IUPAC name is potassium hexacyanoferrate(III). \[ \boxed{\text{(B) }\text{Potassium hexacyanoferrate(III)}} \]