Sciencemadness Discussion Board

NH4OH

kevinlimse - 20-10-2004 at 02:57

Why is the Ammonium Hydroxide an improper name for aqueous ammonia?

kyanite - 20-10-2004 at 12:19

??? Don't those two go interchangeably because it's at an equilibrium? Or atleast in water: NH3 + H2O <--> NH4OH

My guess why ammonium hydroxide isn't the same would be the consetrations. Ammonium Hydroxide(assumed that it's in a pure, not mixture form) isn't the same consentration as aqueous ammonia, which would be NH3 dissolved, and would be at max about 30% NH3?

vulture - 20-10-2004 at 12:51

Because ammoniumhydroxide doesn't exist and can't be isolated.

The correct rxn:

NH3 + H2O ----> NH4+ + OH- which are present as seperate ions.

tom haggen - 21-10-2004 at 10:12

So you if you have a synthesis that calls for a 5% (aq) solution of NH3 than you could simply use ammonium hydroxide. Also If you have a 100% (aq) NH3 is that the same as 100% NH4OH?

vulture - 21-10-2004 at 10:53

100% NH3 can't contain anything else but NH3 and thus can't be a solution....

tom haggen - 22-10-2004 at 08:24

Okay, 99% then. Lets say you dissolve NH3 (g) into H20 up to a 99% concntration. Will it consist of NH4 ions and OH ions floating around in water? Or will there be some definite NH3 ions thrown in the mix? I don't know why but I've had a hard time understanding this concept for sometime now.

[Edited on 22-10-2004 by tom haggen]

vulture - 22-10-2004 at 10:18

The equilibrium NH3 + H2O <---> NH4+ + OH- is situated to the left and even more so in concentrated solutions.

99% NH3 won't work either because that is just humid NH3 gas.

tom haggen - 22-10-2004 at 10:22

Ammonia is one slut of a chemical.
I guess I'm still only used to reactions that theoretically happen from left to right, maybe thats why i'm having such a hard time wrapping my head around this topic.



[Edited on 22-10-2004 by tom haggen]

vulture - 22-10-2004 at 12:00

You should study equilibriums and then acid-base equilibriums, this will give you a much clearer view.

There are not many reactions that go fully to completion.