2 C2-IH2 + O20 4 C0 + 2 H2O-II

This is an oxidation-reduction (redox) reaction:

4 C-I - 4 e- 4 C0 (oxidation)

2 O0 + 4 e- 2 O-II (reduction)

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