Preparation and standardization molar and normal solutions of Potassium permanganate
Potassium permanganate (KMnO4) is a commonly used chemical in analytical chemistry, and it is often prepared in molar or normal solutions for various analytical purposes. Here is a general procedure for preparing and standardizing molar and normal solutions of potassium permanganate:
- Preparation of Molar Solution:
- Calculate the required mass of KMnO4 to prepare the desired molar solution based on the molecular weight of KMnO4 (158.03 g/mol). For example, to prepare a 0.1 M solution of KMnO4, dissolve 1.5803 g of KMnO4 in 1 L of distilled water.
- Dissolve the calculated amount of KMnO4 in a small volume of distilled water in a clean, dry 1 L volumetric flask.
- Add distilled water to the flask until the volume reaches 1 L, and mix thoroughly to ensure uniform distribution of the solute.
- The resulting solution is a 1 M solution of KMnO4.
- Preparation of Normal Solution:
- Calculate the required mass of KMnO4 to prepare the desired normal solution based on the molecular weight of KMnO4 (158.03 g/mol) and the equivalent weight of KMnO4 (31.61 g/equivalent). For example, to prepare a 0.1 N solution of KMnO4, dissolve 0.3161 g of KMnO4 in 1 L of distilled water.
- Dissolve the calculated amount of KMnO4 in a small volume of distilled water in a clean, dry 1 L volumetric flask.
- Add distilled water to the flask until the volume reaches 1 L, and mix thoroughly to ensure uniform distribution of the solute.
- The resulting solution is a 0.1 N solution of KMnO4.
- Standardization:
- Weigh accurately about 0.2 g of sodium oxalate (Na2C2O4) in a clean and dry weighing boat.
- Dissolve the weighed sodium oxalate in a small volume of distilled water in a clean and dry 250 mL Erlenmeyer flask.
- Add 25 mL of dilute sulfuric acid (1:1) to the flask.
- Titrate the solution with the prepared molar or normal solution of KMnO4 until the pink color persists for at least 30 seconds. Note the volume of KMnO4 solution used.
- Repeat the titration two more times to obtain consistent values.
- Calculate the concentration of KMnO4 solution using the following formula:
Molarity of KMnO4 solution = (Weight of sodium oxalate x 2 x Normality of KMnO4) / (Volume of KMnO4 solution x Molecular weight of sodium oxalate)
The standardization process should be repeated periodically to ensure the accuracy of the prepared solution.
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