How do you prepare potassium permanganate? 

Potassium Permanganate (0.02M)

Molecular formula: KMnO4 

Molecular weight: 158.03 

Preparation: Dissolve 3.2 g of potassium permanganate in 1000 mL of water, heat on a water bath for 1 hour; allow standing for 2 days and filtering through glass wool. Store the solution in a dark place, protected from light. 

Standardization: [against sodium oxalate (Na2C2O4)] 

Weigh accurately 0.1 g of dry sodium oxalate dissolved in 80 mL of distilled water, add 5 mL of concentrated H2SO4 cautiously, cool the solution to 25-30°C, and stir until the oxalate has dissolved. Add 90-95% of the required KMnO4 from the burette at a rate of 25-30 mL/minute while stirring slowly, heat the solution to 55-60°C and complete the titration by adding KMnO4 dropwise until a faint pink color persists 30 seconds. 


Na2C2O4 + H2SO4 → H2C2O4 + Na2SO4

5H2C2O4 + 2KMnO4 + H2SO4 → 2MnSO4 + K2SO4 + 10CO2 + 8H2

Factor Calculation: 

2 moles of KMnO4 ≅ 5 moles of sodium oxalate 

2000 mL of 1M KMnO4 ≡ 5 × 133.98 g of Na2C2O4 

1 mL of 0.02 M KMnO4 0.0067 g of Na2C2O4  

Standardization: [against sodium thiosulphate (Na2S2O3)] 

To 25.0 mL of the KMnO4 solution in a glass-stoppered flask add 2 g of potassium iodide, followed by 10 mL of 1 M sulphuric acid. Titrate the liberated iodine with 0.1 M sodium thiosulphate, using 3 mL of starch solution, added towards the end of the titration, as an indicator. Perform a blank determination and make the necessary correction. [liberated iodine makes sample solution dark brown, when I2 is titrated with sodium thiosulphate, I2 is reduced to iodide which is a colorless species, thus the color of the solution fades slowly as titration proceeds and when it becomes yellowish indicates the endpoint is nearer and then the starch solution (indicator) is added]. 


2KMnO4 + 10KI + 8H2SO4 → 5I2 + 2MnSO4 + K2SO4 + 8H2

[2Na2S2O3 + I2 → Na2S4O6 + 2NaI] 

Factor Calculation: 

5 moles of iodine ≅ 2 moles of KMnO4 

1 mole of I2 ≅ 0.4 mole of KMnO4


[1 mole of I2 ≅ 2 moles of Na2S2O3

2 moles of Na2S2O3 ≅ 0.4 mole of KMnO4 

2000 mL of 1M Na2S2O3 ≅ (0.4 × 158.03 = 63.202 g) of KMnO4 

1 mL of 0.1 M Na2S2O3 ≅ 0.003161 g of KMnO4

Make sure you also check our other amazing Article on: How do you make lithium methoxide (0.1M)?
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