2 Cr(NO3)3 (aq) + 3 Br2 (aq) + 14 KOH (aq) → K2Cr2O7 (aq) + 6 KBr (aq) + 6 KNO3 (aq) + 7 H2O (l)
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, Cr(NO3)3 is a reducing agent.