Calculate the oxidation number of carbon ( C ) in **H _{2}C_{2}O_{4}** .

let us consider the oxidation number of carbon to be x.

also, we know that the oxidation number of hydrogen be +1 and Oxygen be -2.

(+1) × 2 + ( x ) × 2 + ( -2 ) × 4 = 0

+2 + 2x – 8 = 0

2x = + 6

x = + 3

Hence, the oxidation state of C in **H _{2}C_{2}O_{4}** is +3.