The reaction between potassium permanganate (KMnO₄) and oxalic acid (H₂C₂O₄) is a second-order reaction.

Here's why:

* Mechanism: The reaction proceeds in two steps:

1. Slow step: The permanganate ion (MnO₄^-) reacts with oxalic acid to form manganese(II) ions (Mn²⁺) and carbon dioxide (CO₂). This step is the rate-determining step, meaning it's the slowest step and controls the overall reaction rate.

2. Fast step: The manganese(II) ions react with excess permanganate ions to form more manganese(II) ions and carbon dioxide.

* Rate Law: The rate law for the reaction is:

Rate = k[KMnO₄][H₂C₂O₄]

where:

* k is the rate constant

* [KMnO₄] is the concentration of potassium permanganate

* [H₂C₂O₄] is the concentration of oxalic acid

* Order: The rate law shows that the reaction is first-order with respect to both potassium permanganate and oxalic acid. Since the overall order is the sum of the individual orders, the reaction is second-order overall.

Important Note: The reaction is also influenced by other factors like temperature and the presence of a catalyst (such as sulfuric acid).