MnO2 + 2 KBr2 + 2 H2SO4 → MnSO4 + 2 Br2 + K2SO4 + 2 H2O
This is an oxidation-reduction (redox) reaction:
4 Br-I - 4 e- → 4 Br0 (oxidation)
MnIV + 2 e- → MnII (reduction)
2 KII + 2 e- → 2 KI (reduction)
KBr2 is a reducing agent, MnO2 is an oxidizing agent, KBr2 is an oxidizing agent.