Answer
See answer below.
Work Step by Step
First hydronium:
$H_2C_2O_4(aq)+H_2O(l)\rightarrow HC_2O_4^-(aq)+H_3O^+(aq)$
Second hydronium:
$HC_2O_4^-(aq)+H_2O(l)\rightarrow C_2O_4^{2-}(aq)+H_3O^+(aq)$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.