[DTU student #12]

Hello, I have a question about the equilibrium between gasseous ammonia, absorbed ammonia (in acidic solution) and ammonium ions. The question relates from an acid trap / dilution trap

I know that gasseous ammonia is very soluble in water, at 31wt% at 25°C. I know that the absorption of gasseous ammonia into the waterphase of an acidic solution is described by Henrys law. 

My question is about the capacity of the acid trap. It revolves around the following equilibrium NH₃  NH₄⁺
that will exist in the acidic solution, and likely be pushed far to the right.
If the solubility of ammonia in the waterphase is 31wt%, does those 31wt% include both the NH₃ and NH₄⁺ ?
Such that the absorption capacity of the acid trap is the same as that for water, and the only "difference" is the acidic enviroment, that protonates ammonia, in order to keep it from escaping the waterphase?

My thoughts about it, is that in one way, the solubility is given for NH₃ , which kind of excludes NH₄⁺, but then again, ammonia and ammonium is also sort of the same chemical? I am leaning towards the answer, that the 31wt% includes both NH₃ and NH₄⁺

Any help / confirmation will be greatly appreciated
Best Regards

[DTU student #12]

Sorry for the bad "language" in the original post, english is not my native language.

To clarify, I am basically asking that when I look at the solubility of gasseous ammonia in water, it is 31% weight to weight at 25°C. I am trying to figure out, whether both the NH₃ and NH₄⁺ of the equilibrium NH₃ NH₄⁺ are included in this solubility percent?

And if it is so, will adding a strong acid like sulfuric acid, do nothing but push that equilibrium very far to the right? Or will it also, somehow, raise the solubility percentage?

I think that it won't raise the solubility, but only affect the equilibrium, but I am unsure because the solubility I found was named "solubility for NH₃ in water" and not NH₃+NH₄⁺

Again, sorry for the confusion / poorly written original question.

Any help will be greatly appreciated

[Borek]

If solubility is given as 31% it most likely means just ammonia and water - so yes, it includes the "natural" equilibrium between NH₃ and NH₄⁺ but without any acid added.

Adding an acid may help - but hard to say to what extent, behavior of concentrated solutions is rather difficult to predict.

[DTU student #12]

Thank you for your reply, it was very useful / helpful 

My question has its base in some smaller calculations for an theoretical estimate of maximum absorption capacity of gasseous ammonia in activated carbon impregnated with phosphoric acid, which was also investigated experimentally.

Unfortunately Murphy's first law had a very big influence in the study, and the results were some what inconclusive. I think that, to some extent, the phosphoric acid might have raised the absorption capacity, but the results are too inconclusive to say for sure.

edit*

Sorry if this is a dumb question, but what is it that makes it hard to predict the behavior of concentrated solutions? Is it because of increased ionic stenght, or because of interactions between solute/solute, rather than just solute/solvent interactions as in dilute solutions?

Best Regards

[Borek]

Unfortunately Murphy's first law had a very big influence in the study, and the results were some what inconclusive. I think that, to some extent, the phosphoric acid might have raised the absorption capacity, but the results are too inconclusive to say for sure.

Actually I was going to suggest experiment as the only sure way of checking.

If the result is inconclusive it most likely means the difference is small (regardless of what it really is).

Sorry if this is a dumb question, but what is it that makes it hard to predict the behavior of concentrated solutions? Is it because of increased ionic stenght, or because of interactions between solute/solute, rather than just solute/solvent interactions as in dilute solutions?

All of those. Basically 30% w/w water solution is no longer a "water solution" - it is a mixture containing water as one of the main components, which makes calculations much harder.