2 C2-IH2 + 3 O20 4 CIIO-II + 2 H2O-II

This is an oxidation-reduction (redox) reaction:

4 C-I - 12 e- 4 CII (oxidation)

6 O0 + 12 e- 6 O-II (reduction)

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