Volumetric Analysis of Ammonia
You will measure the ammonia content of the product with a simple but colorful titration. A standard HCl solution will be provided to titrate all the ammonia contained in a sample of your copper(II) compound. Since this is a strong acid-weak base titration, the equivalence point occurs at pH < 7, and methyl orange is a good indicator to use. Methyl orange changes from orange-yellow to red at the endpoint of the titration; however, due to the brightly colored copper(II) compounds produced during the titration you should observe several interesting color changes. The solution starts out deep blue becomes a blue-green suspension, and then a pea-green suspension when 70% of the HCl has been added. By the time 85% of the acid has been added, the suspension is golden yellow. The endpoint occurs when the suspension becomes a pumpkin-orange solution. A red-orange solution is passed the endpoint.