If the solution contains NH4HCO3, (NH4)2CO3, and NH3, how can the concentrations of each component be determined?

This is the ionization equilibrium of a salt formed from a weak acid and a weak base, and it requires the use of multiple charge balances and mass balances to be calculated. Since the entire ionization process is not ideal and perfect, the amount of each component can only be determined by measuring the total amount. Divide the sample into two parts. Distillation is carried out with an excess of strong base; the distillate is collected and absorbed using a weak acid, after which the ammonia content is determined by an ammonia detection method. Another method involves adding an excess of barium hydroxide solution, which causes the carbonate and bicarbonate ions to form barium carbonate precipitate; the precipitate is separated, then dissolved using hydrochloric acid. After adjusting the pH to alkaline levels, standard EDTA solution is added, thereby allowing the total amount of carbonate ions to be determined.

Thank you for the reply from above! There are a few things I don’t understand: does the test for strengthening the alkali measure the ammonia content? The strong base converts ammonium ions into ammonia gas; isn’t what’s being measured the total ammonia content? Another standard EDTA solution adjusted to an alkaline ammonia level can be used to determine the carbonate content; I don’t understand what this sentence means.

What is measured is the total ammonia content. An excess of barium hydroxide solution is added, and finally EDTA is used to determine the amount of excess barium; based on the total amount of barium initially added, the total amounts of carbonate and bicarbonate can be calculated. Furthermore, if there is a large amount of NH3 in the system, it is worth considering whether a large amount of bicarbonate can exist and whether carbonate will be formed. Of course, we can look up the equilibrium constant and carry out a calculation. The above is for reference only.

Distillation is carried out with an excess of strong base; the distillate is collected and absorbed using a weak acid, after which the ammonia content is determined by an ammonia detection method. Another method involves adding an excess of barium hydroxide solution, which causes carbonate and bicarbonate ions to form barium carbonate precipitate; the precipitate is separated, then dissolved using hydrochloric acid. After adjusting the pH to alkaline levels, standard EDTA solution is used to determine the total amount of carbonate ions