C2H2 + K2Cr2O7 + 2 H2SO4 → Cr2SO4 + K2SO4 + 2 CO2 + 3 H2O
This is an oxidation-reduction (redox) reaction:
2 C-I - 10 e- → 2 CIV (oxidation)
SVI + 4 e- → SII (reduction)
2 CrVI + 6 e- → 2 CrIII (reduction)
C2H2 is a reducing agent, H2SO4 is an oxidizing agent, K2Cr2O7 is an oxidizing agent.