How do I balance the equation for the oxidation of diphenylcarbazide by Cr⁶⁺ to give diphenylcarbazone and Cr³⁺?

1 Answer
Dec 4, 2014

Answer:

The easiest way is to use the ion electron method.

Explanation:

Here are the steps.

Net ionic equation

Cr₂O₇²⁻ + C₆H₅NHNHCONH-NHC₆H₅ → Cr³⁺ + C₆H₅NHNHCON=NC₆H₅

Skeleton half–reactions

Cr₂O₇²⁻ → Cr³⁺
C₆H₅NHNHCONH-NHC₆H₅ → C₆H₅NHNHCON=NC₆H₅

Balanced half-reactions

Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O
C₆H₅NHNHCONH-NHC₆H₅ → C₆H₅NHNHCON=NC₆H₅ + 2H⁺ + 2e⁻

Equalize electrons transferred

1 × [Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O]
3 × [C₆H₅NHNHCONH-NHC₆H₅ → C₆H₅NHNHCON=NC₆H₅ + 2H⁺ + 2e⁻]

Add half-reactions

Cr₂O₇²⁻ + 3C₆H₅NHNHCONH-NHC₆H₅ + 8H⁺ → 2Cr³⁺ + 3C₆H₅NHNHCON=NC₆H₅ + 7H₂O

Add spectator ions

K₂Cr₂O₇ + 3C₆H₅NHNHCONH-NHC₆H₅ + 4H₂SO₄ → Cr₂(SO₄)₃ + 3C₆H₅NHNHCON=NC₆H₅ + K₂SO₄ + 7H₂O