2 Cr(OH)3 + 4 NaOH + 3 H2O2 → 2 Na2CrO4 + 8 H2O
This is an acid-base reaction (neutralization): Cr(OH)3 is an acid, NaOH is a base.
This is an oxidation-reduction (redox) reaction:
2 CrIII - 6 e- → 2 CrVI (oxidation)
6 O-I + 6 e- → 6 O-II (reduction)
Cr(OH)3 is a reducing agent, H2O2 is an oxidizing agent.