Final answer:
In the titration of potassium permanganate and oxalic acid, the oxidation number of carbon changes from +3 in oxalic acid to +4 in the product carbon dioxide at the end point.
Step-by-step explanation:
The question relates to the titration of potassium permanganate (KMnO₄) and oxalic acid (H₂C₂O₄) in an acidic medium, and asks about the change in the oxidation number of carbon at the end point. In the balanced redox reaction, where 2 moles of KMnO₄ react with 5 moles of oxalic acid, the oxidation number of carbon in oxalic acid changes as follows:
- Before the titration, oxalic acid (H₂C₂O₄) has the carbon in a +3 oxidation state.
- During the titration, oxalic acid is oxidized, and carbon ends up in carbon dioxide (CO₂), where it has an oxidation number of +4.
Therefore, the change in the oxidation number of carbon at the end point of the titration is from +3 to +4.