Cr2(SO4)3 + 5 KI + KIO3 + 3 H2O → 2 Cr(OH)3 + 3 K2SO4 + 3 I2
This is an oxidation-reduction (redox) reaction:
5 I-I - 5 e- → 5 I0 (oxidation)
IV + 5 e- → I0 (reduction)
KI is a reducing agent, KIO3 is an oxidizing agent (synproportionation (comproportionation)).