When preparing a solution of potassium permanganate (KMnO4), it is recommended to use dust-free water that has been freshly boiled and cooled for a few reasons:
Dust-free water: Dust particles present in water can interfere with the accuracy of the solution's concentration. Dust may contain organic and inorganic impurities that can react with KMnO4 or affect the stability of the solution. To ensure the reliability and consistency of the solution, it is best to use water that is free from visible particles.
Boiling and cooling: Boiling the water serves multiple purposes:
a. Sterilization: Boiling water helps to kill any microorganisms or bacteria present in the water. It reduces the risk of microbial contamination, which could potentially interfere with the reaction or introduce unwanted substances into the solution.
b. Removal of dissolved gases: Boiling water removes dissolved gases such as carbon dioxide. These gases can react with KMnO4, altering its concentration and affecting the accuracy of the solution.
c. Oxygen removal: Boiling water expels dissolved oxygen. Oxygen can potentially react with KMnO4, reducing its oxidizing properties and affecting the desired reaction outcome.
Cooling the boiled water is necessary to reach a suitable temperature for preparing the solution. Extreme temperatures, whether too hot or too cold, can affect the solubility and stability of KMnO4.
By using dust-free and freshly boiled water, the risks of introducing impurities or unwanted reactions that could alter the concentration or properties of the KMnO4 solution are minimized. This ensures the accuracy and reliability of the solution for various applications, such as titrations or other chemical reactions.