In the reaction, C2O2−4 → CO2 , the total number of electrons lost per mole of C2O−24 is
2N
Oxidation state of ‘C’ in C2O2−4=+3 & Oxidation state of ‘C’ in CO2=+4
Change in oxidation state of ‘C’ = 4 – 3 = 1
Since there are two ‘C’ atoms in C2O2–4 ; Number of electrons transferred = 2 x 1 = 2 e