Potassium permanganate (KMnO4) is a strong oxidizing agent commonly used in analytical chemistry for titrations. Here’s how to prepare and standardize both molar (1.0 M) and normal (1.0 N) solutions of potassium permanganate.
Preparation of 1.0 M Potassium Permanganate Solution:
A 1.0 M potassium permanganate solution contains one mole of KMnO4 in one liter.
Materials Required:
– Potassium permanganate crystals (KMnO4)
– Distilled water
– A balance
– A glass stirring rod
– A glass or plastic container
– A 1.0 L volumetric flask
Procedure:
1. Weigh out the required amount of potassium permanganate crystals (158.04 g/mol) to make a 1.0 M solution. To prepare 1.0 L of 1.0 M KMnO4 solution, you’ll need 158.04 grams of KMnO4. Ensure that the substance is accurately weighed.
2. Transfer the weighed KMnO4 crystals into a clean, dry glass or plastic container.
3. Add distilled water to the container and stir the mixture with a glass stirring rod until the KMnO4 crystals completely dissolve. The final volume of the solution should be less than 1.0 L at this stage.
4. Transfer the solution into a 1.0 L volumetric flask. Rinse the container with distilled water to ensure all the KMnO4 is transferred to the flask.
5. Fill the volumetric flask to the 1.0 L mark with distilled water while maintaining the temperature at a consistent level (usually 20°C). The solution is now a 1.0 M potassium permanganate solution.
Standardization of 1.0 M Potassium Permanganate Solution to Prepare 1.0 N Solution:
To standardize the 1.0 M KMnO4 solution and prepare a 1.0 N solution, you’ll need to determine its exact molar concentration.
Materials Required:
– A primary standard reagent, such as oxalic acid (C2H2O4)
– Sulfuric acid (H2SO4)
– A burette
– A balance
– A 1.0 L volumetric flask
Procedure:
1. Weigh out a sample of a primary standard reagent, such as oxalic acid (C2H2O4) of known purity. Accurately weighs about 1.574 g of C2H2O4. The molar mass of C2H2O4 is 90.04 g/mol.
2. Dissolve the weighed C2H2O4 in distilled water and transfer it into a 1.0 L volumetric flask.
3. Add a few drops of sulfuric acid (H2SO4) to the C2H2O4 solution. The sulfuric acid is added to acidify the solution and prevent the reduction of KMnO4 by any impurities or substances in the solution.
4. Prepare the burette with the 1.0 M KMnO4 solution.
5. Titrate the C2H2O4 solution with the KMnO4 solution until the purple color of the KMnO4 solution persists, indicating that all the C2H2O4 has reacted.
6. Record the volume of KMnO4 solution used for the titration. Use this volume to calculate the exact molar concentration of the KMnO4 solution.
7. If the calculated molarity is very close to 1.0 M, the solution can be considered a 1.0 N potassium permanganate solution. If not, adjust the concentration and re-standardize if necessary.
