H2C2O4 (aq) → H2O (l) + CO2 (g) + CO (g)
This is an oxidation-reduction (redox) reaction:
CIII + e- → CII (reduction)
CIII - 1 e- → CIV (oxidation)
H2C2O4 is both an oxidizing and a reducing agent (disproportionation (dismutation)).
This is a gas evolution reaction, CO2 and CO is the formed gas.