C2H2 + K2Cr2O7 → CrCO3 + Cr + K2CO3 + H2O
This is an oxidation-reduction (redox) reaction:
C-I - 5 e- → CIV (oxidation)
C-I - 4 e- → CIII (oxidation)
CrVI + 6 e- → Cr0 (reduction)
CrVI + 3 e- → CrIII (reduction)
C2H2 is a reducing agent, C2H2 is a reducing agent, K2Cr2O7 is an oxidizing agent, K2Cr2O7 is an oxidizing agent.