10 BiBr5 + 6 KMnO4 + 24 H2SO4 → 5 Bi2(SO4)3 + 6 MnSO4 + 3 K2SO4 + 24 H2O + 25 Br2
This is an oxidation-reduction (redox) reaction:
50 Br-I - 50 e- → 50 Br0 (oxidation)
6 MnVII + 30 e- → 6 MnII (reduction)
10 BiV + 20 e- → 10 BiIII (reduction)
BiBr5 is a reducing agent, KMnO4 is an oxidizing agent, BiBr5 is an oxidizing agent.