Aim: To prepare and submit 100 ml of a strong solution of ammonium acetate.
Requirement: Ammonium bicarbonate, Glacial acetic acid, Strong ammonia solution, Beaker, Glass rod, Measuring cylinder, Purified water, etc.
Theory: Strong solution of ammonium acetate contains 57.5% w/v of ammonium acetate and it is prepared by reacting glacial acetic acid with ammonium bicarbonate and a strong solution of ammonia.
NH4HCO3 + CH3COOH → (CH3COO)NH4 + H2O + CO2
It is not possible to prepare the solution by reacting glacial acetic acid with ammonium bicarbonate alone because the reaction between these substances ceases before the formation of the required amount of ammonium acetate. In this reaction the formation of ammonium acetate is enhanced, the concentration of acetate ions increases and the ionization of acetic acid decreases.
Glacial acetic acid cannot be replaced with acetic acid because glacial acetic acid is 99% pure, while acetic acid is only 33% pure. This preparation can be prepared using ammonia strong solution alone because 453 g of glacial acetic acid is neutralized with about 1000 ml. Ammonium hydroxide is used to neutralize the unreacted acid and to make the preparation alkaline with a pH range of 7.6 to 8.1. The pH is adjusted by using two indicators like bromothymol blue and thymol blue.
|Glacial acetic acid
|Strong ammonia solution
- Dissolve ammonium bicarbonate by adding gradually it to the glacial acetic acid diluted with 350 ml of purified water.
- Add ammonium bicarbonate in a small amount at a time until it is completely dissolved.
- Add strong ammonia solution until 0.05 ml of the resulting solution diluted with 0.5 ml of water gives a full blue color with 0.05 ml of bromothymol blue solution and full yellow color with 0.05 ml of thymol blue solution.
- Add a sufficient amount of purified water to produce 1000 ml.
Storage: Keep in a tightly closed container (lead-free glass containers). Store in a cool, dry, ventilated area.
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