Balance the following redox reaction in acid. You must show all your work.

Question

Balance the following redox reaction in acid. You must show all your work.

C₃H₄O₂^3- + Cr⁶⁺ → Cr + CO

Answer 1

C₃H₄O₂^3- + Cr⁶⁺ → Cr + CO

Cr⁶⁺ ==> Cr

Cr⁶⁺ + 6e- ==> Cr ... balanced reduction half reaction

C₃H₄O₂^3- ==> CO

C₃H₄O₂^3- + H₂O ==> 3CO ... balanced for C and O

C₃H₄O₂^3- + H₂O ==> 3CO + 6H⁺ ... balanced for C, O and H (using acid, H⁺)

C₃H₄O₂^3- + H₂O ==> 3CO + 6H⁺ + 9e- ... balanced for C,O,H and charge = balanced oxidation half rxn

To equalize electrons, multiply reduction rxn by 3 and oxidation rxn by 2:

3Cr⁶⁺ + 18e- ==> 3Cr

2C₃H₄O₂^3- + 2H₂O ==> 6CO + 12H⁺ + 18e-

Add these together and combine/cancel like terms to obtain the final redox equation:

3Cr⁶⁺ + 2C₃H₄O₂^3- + 2H₂O ==> 3Cr + 6CO + 12H⁺ ... balanced redox equation