[HP]

Hi,
Sorry for my ignorance in general chemistry but i have this following mind problem:
I know that aqueous amonia is somethink like a mixture of H2O, amonium hydroxyde(NH4+ OH-) and molecular amonia (NH3). Molecular amonia is a weak base i agree but Arenius and Bronsted theory said that NH4OH is a weak base because in H2O its not fully dissociated nad heres the problem: First theres two paralel processes - if theoretically some chemist may obtain at some conditions for some time free and pure NH4OH(as a solid for example) and disolve it in water then the i think it will first fully disociate at NH4 + and OH- and for the time it happen it will be as strong(by definition) base as NaOH for example. In the next moment as unstable compound NH4+ OH could exist in equilibrium with the molecular NH3 and H2O - this i call disprpotion reaction and then NH4OH become a weak base by definition. Of course as much amonia we have in water as much and OH and the media become fairly basic(as i know some aqueous solutions amonia are strongly basic with pH=13). My question is if theres some extreme conditions as for example high pressures or low temperatures or both:) when chemists may say: "here you are your fully disociated NH4+OH- with no free NH3 and this is definetely a strong base by definition and the solution is strong beasic too"
Have any chemist isolated fully disociated NH4+ OH in water or other media or NH4OH as molecule ? Do someone think chemistry is science of exceptions...
Sorry if my questions sound mad but when i see in books that amonia is a weak base i have some doubts about this definition )
Help me urgent please!
Ths

[Albert]

Maybe, according to Le Chatelier's principle, adding a strong acid, such as HCl, you may have a solution which contains NH4Cl and water only.

[HP]

Aha i wrote that at physiological pH=7 abot 99% of dissolved NH3 is present in the form of ammonium ions(NH4+). Then i suppose if  the counter-ions are OH- then NH4OH at pH = 7 should be a strong base by deffinition as fully dissociated am i right? The paradox for me is that as the media become much and much basic the equilibrium turn left to the free molecular NH3. I am still looking for conditions at which NH4OH have behaviour of a strong base: I know that at extreemely high pressures scientists has obtained ice which may exist as ice only at temperature of boiling water (the so known ice 7) - if the same procedure be done with aqueous ammonia do you think the obtained solid will smell on ammonia at normal presure and some temperature and if not may be the obtained solid will be the hypothetic strong base NH4OH   The last is a speculation i think but continue thinking..

[Borek]

if theoretically some chemist may obtain at some conditions for some time free and pure NH4OH(as a solid for example)

So far nobody did it, so problem doesn't exist.

and disolve it in water then the i think it will first fully disociate at NH4 + and OH-

It will rather decompose into NH₃ and H₂O directly, without being strong base for a moment. Much simpler and much more likely.

[HP]

Thank you for the reply Borek!
I will also be very happy if some day some colegue isolate and demonstrate the existent of pure individual compound NH4OH then i'll be very happy too It's really from interest how it will disolve in water and i think you are probably right as thinkink for the easy decomposition reaction occurs then...Now when we hjave discussed the proble it alredy exist in the universe i say:))
I have another question: Whats the reason that when completely dry NH3 mixed with completely dry HCl no smoke reaction to NH4Cl occur  

[jdurg]

Yes, in reality NH4OH simply does not exist.  When NH3 is dissolved in water, you simply get NH4+ ions, OH- ions, and dissolved NH3 molecules.  At no point in time does NH4OH form.  Instead, you get the NH3 molecules attaching to a free H+ forming NH4+ and leaving OH- behind in solution.  Because of LeChatellier's principle, this causes more water to break apart into H+ and OH- ions allowing more NH4+ to form until an overall equillibrium is reached.

It's a shame that in schools they still teach people that ammonia solutions are NH4OH because that simply isn't true.  NH4OH just does not exist.  Think about what the structure of it would be.  You'd have to have five bonds with a central nitrogen atom in order for it to exist and that simply just won't happen.

[HP]

Hehe i was shamed by the same thing friend! It's a rather fatal mistake to write in books that i citate:"NH4OH is a weak base" as this compound as i know doesent exist in its molecular form as we all know NaOH, KOH do ..but only in dissociated NH4+ and OH- form! I am not specialist in inorganic chemistry but can i  do analogy in the structure of the hypothetical molecule NH4OH with the real NH4Cl for example following the Panet-Faians rule? In fact i still artlessly believe that somewhere in the Universe NH4OH exist in molecular form - be it and for a second and the conditions for it existence are in chemists hands or in physicist eyes  Following the  LeChatellier's-Brown principle is there such a conditions like  high or low pressure and temperature(-/+) when all the NH3 molecules to react with H2O and then in the system NH4+ and OH- or even NH4OH exist? What in fact cosmic chemistry say the problem ?
Thanks for all the replies they make me calm
P.S.Pls  find these my posts fun- more like play of words with some selfirony...