8 H3O+ + 3 SO32- + Cr2O72- → 2 (Cr)3+ + 3 SO42- + 12 H2O
This is an oxidation-reduction (redox) reaction:
3 SIV - 6 e- → 3 SVI (oxidation)
2 CrVI + 6 e- → 2 CrIII (reduction)
SO32- is a reducing agent, Cr2O72- is an oxidizing agent.
Reactants:
Products: