Writing equation of reaction in stoichiometry of redox titrations While solving some questions on the stoichiometry on redox titrations, I come across this question:


  Calculate the volume of $0.05\ \mathrm{M} \ \ce{KMnO4}$ solution required to oxidize completely $2.70\ \mathrm{g}$ of oxalic acid in acidic medium.  


I know how to solve this question. The only problem I am facing is that the reaction equation is not given. How do I know what the products of this reaction would be? Can someone help me in how to write the equation of the reaction by the information given in the question.
See the following steps:


We know what $\ce{KMnO4}$ will do by reading the question:


  Calculate the volume of […] $\ce{KMnO4}$ solution required to oxidize completely […] oxalic acid.

We need the structure of oxalic acid. (This is knowledge required to answer the question, no way around.)


Structure of oxalic acid. Image taken from Wikipedia, where a full list of authors is available.
Determine oxidation numbers of all the atoms involved. Shortcut: hydrogen has $\mathrm{+I}$, oxygen has $\mathrm{-II}$ and carbon has $\mathrm{+III}$.
Determine what can be oxidised. Only carbon really can.
Determine what it can be oxidised to. The final product must have $\ce{C^{IV}}$, which is most common as carbon dioxide or carbonate.
Solve the redox equation using either $\ce{CO2}$ or $\ce{CO3^2-}$. Both will work.