C2H2 (g) + 2 O2 (g) → H2 (g) + 2 CO2 (g)
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.