10 KOH (aq) + 3 Br2 (aq) + Cr2O3 (s) → 5 H2O (l) + 6 KBr (aq) + 2 K2CrO4 (aq)
This is an oxidation-reduction (redox) reaction:
6 Br0 + 6 e- → 6 Br-I (reduction)
2 CrIII - 6 e- → 2 CrVI (oxidation)
Br2 is an oxidizing agent, Cr2O3 is a reducing agent.