Explanation:
Firstly, let us state the reactants and products involved in the chemical reaction of an acid with a base.
After having obtained our neutral potassium hydroxide solution (KOH), it is imperative to separate water from the solution so as to proceed with crystallisation process.
1. Heat the solution in an evaporating dish so as to evaporate the water molecules in it.
STEPS:
(i) Set up your tripod stand onto which you should place your wire gauze. Place a beaker of hot water on the wire gauze and the evaporating dish containing KOH on the surface of the beaker. Light the bunsen burner and wait for bubbles and steam to form. The water in the beaker should boil at 80°c.
2. Steam will rise from the boiling water and will come in contact with the KOH solution. The water which was formed as a product from the initial reaction in the KOH, will gradually evaporate due to it being heated on a water bath.
3. Once the water molecules from the KOH solution had evaporated, KCl would have formed.
Crystallization:
If the KCl obtained is in solution form after evaporation, you can induce crystallization by cooling the solution. As the temperature decreases, KCl will start to crystallize out of the solution.Filtration: Once crystallization is complete, separate the solid KCl crystals from the remaining liquid (mother liquor) using filtration. Use a fine filter paper or a Buchner funnel with vacuum filtration to achieve this.
Washing:
Wash the KCl crystals with a small amount of cold, distilled water to remove any adhering impurities. This step helps to purify the KCl further.
Drying:
Dry the purified KCl crystals. This can be done by placing them in a drying oven at a moderate temperature or by allowing them to air dry in a desiccator. Avoid high temperatures to prevent decomposition (You can dry the crystals by placing them between sheets of tissue paper as well.)
