C2-IH2I + 2 O20 H20 + 2 CIVO2-II

This is an oxidation-reduction (redox) reaction:

2 C-I - 10 e- 2 CIV (oxidation)

2 HI + 2 e- 2 H0 (reduction)

4 O0 + 8 e- 4 O-II (reduction)

C2H2 is a reducing agent, C2H2 is an oxidizing agent, O2 is an oxidizing agent.