H2SO4 + 10 HI + 2 KIO3 → 6 H2O + K2SO4 + 6 I2
This is an oxidation-reduction (redox) reaction:
10 I-I - 10 e- → 10 I0 (oxidation)
2 IV + 10 e- → 2 I0 (reduction)
HI is a reducing agent, KIO3 is an oxidizing agent (synproportionation (comproportionation)).