Introduction
This titration involves the redox reaction between oxalic acid (H₂C₂O₄) and acidified potassium permanganate (KMnO₄). It is used to determine the concentration or purity of oxalic acid and requires heating to initiate the reaction.

🔹 Reaction Principle

KMnO₄ acts as an oxidizing agent and oxidizes oxalic acid to carbon dioxide in acidic medium.

Balanced Ionic Equation:

🔹 Theory

• KMnO₄ (purple) is reduced to Mn²⁺ (colorless/pale pink)

• Oxalic acid is oxidized to CO₂ gas

• The reaction is slow at room temperature, so the solution must be heated to ~60°C before titration

• The endpoint is indicated by the first permanent pale pink color

🔹 Apparatus and Chemicals

• Burette, pipette, conical flask, beaker, thermometer

• 0.0200 M KMnO₄ (in burette)

• Oxalic acid solution (in flask)

• Dilute H₂SO₄ (for acidification)

• Hot water bath or heating source

🔹 Procedure

1. Rinse and fill the burette with KMnO₄ solution

2. Pipette 25.00 mL of oxalic acid solution into a conical flask

3. Add about 10 mL of dilute H₂SO₄

4. Heat the solution to ~60°C (not boiling)

5. While hot, titrate with KMnO₄ slowly, swirling the flask constantly

6. Stop when a faint pink color remains for at least 30 seconds

7. Record initial and final burette readings

8. Repeat for consistent (concordant) results

🧠 Calculation Example

Given:

• Volume of KMnO₄ used = 25.40 mL

• Concentration of KMnO₄ = 0.0200 M

• Volume of oxalic acid = 25.00 mL

Balanced mole ratio:
2MnO₄⁻ : 5H₂C₂O₄

Step 1: Moles of KMnO₄

Step 2: Moles of H₂C₂O₄

Step 3: Concentration of oxalic acid

✅ Answer: Oxalic acid concentration = 0.0508 mol/dm³

🔹 Observations

• Before titration: KMnO₄ is purple; solution is colorless

• During titration: Color disappears with each drop

• Endpoint: Pale pink color persists for 30 seconds

• Gas evolution: CO₂ bubbles may be seen during titration

🔹 NECTA Tips

• Always heat oxalic acid before titration

• Do not boil; 60–70°C is sufficient

• Use a white tile to detect color change easily

• Ensure all readings are recorded to 2 decimal places

✅ Summary

• Oxalic acid is titrated against KMnO₄ in acidic, heated conditions

• Reaction requires heat to proceed at a reasonable rate

• End point = permanent pale pink

• Always balance using 2MnO₄⁻ : 5H₂C₂O₄ mole ratio

• Commonly tested in NECTA Chemistry practical exams