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Author: Subject: Make Ammonia gas
TheAMchemistry87
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[*] posted on 4-7-2012 at 11:04
Make Ammonia gas


I wanted to make ammonia gas by adding a conc. NaOH solution to a NH4Cl solution will the Ammonia gas stay in solution as Ammonium hyroxide or Ammonia gas will come out? or also can i heat the solution to evolve ammonia gas? Because i believe that ammonium hyroxides is unstable


-AMchemistry

[Edited on 4-7-2012 by TheAMchemistry87]
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vmelkon
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[*] posted on 4-7-2012 at 11:17


It will stay in solution but it will smell like ammonia indicating that gas is slowly coming off. If you wanna make ammonia gas, mix solid NaOH and NH4Cl.

You can even use NaHCO3 instead of NaOH. NH4HCO3 forms but tends to decompose quickly. I know because I tried it with NaHCO3 and NH4NO3.
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kavu
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[*] posted on 4-7-2012 at 11:18


The solution is basic and drives the equilibrium H₂O + NH₄⁺ ⇆ H₃O⁺ + NH₃ to right. Also the solution heats up a bit from the exothermic reaction and dissolved ammonia is driven out.

[Edited on 4-7-2012 by kavu]
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Rogeryermaw
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[*] posted on 4-7-2012 at 11:47


mix dry chemicals and add a few drops of water. there will be less water of solution for the evolved ammonia gas to dissolve into.
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Endimion17
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[*] posted on 4-7-2012 at 14:09


you can also add a strong base to the concentrated solution of ammonia. it shifts the equilibrium and pushes the gas out.



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Rogeryermaw
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[*] posted on 4-7-2012 at 14:44


or you could try ammonium carbonate available anywhere as "baker's ammonia". it releases ammonia gas and carbon dioxide gas upon heating. no mixing of chemicals required.
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plastics
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[*] posted on 4-7-2012 at 23:53


solid NaOH + solid (NH4)2SO4 + couple of drops of water works fine; gentle heating as the reaction proceeds is needed to maintain a good stream. Gentle heating of concentrated ammonia solution also works very well
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RadioTrefoil
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[*] posted on 18-7-2012 at 03:41


It cannot stay in solution as ammonium hydroxide, there is an equilibrium NH4OH <-> NH3 + H2O that in this case is strongly shifted to the right. You will definitely get ammonia gas from NH4Cl + NaOH.



MESITYL FREAKING OXIDE
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Nicodem
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[*] posted on 18-7-2012 at 09:47


Quote: Originally posted by RadioTrefoil  
It cannot stay in solution as ammonium hydroxide, there is an equilibrium NH4OH <-> NH3 + H2O that in this case is strongly shifted to the right. You will definitely get ammonia gas from NH4Cl + NaOH.

It does not need to stay in solution as "ammonium hydroxide", because there is no such thing anyway. It stays in solution as dissolved ammonia and ammonia is well soluble in aqueous solutions.
Dissolving NaOH in aqueous ammonia does reduce its solubility because NaOH consumes plenty of water for its solvation, but so do other salts in general. The basicity has a pretty much insignificant effect per se.
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[*] posted on 18-7-2012 at 10:59


What about urea and a base, like Ca(OH)2?

CaO would be even better because it binds water.
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ChemistryGhost
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[*] posted on 30-7-2012 at 03:12


Try mixing Ammonium Nitrate(aq) and Sodium Hydroxide(aq)! The ammonium ions will react with the hydroxide and change into anhydrous ammonia in solution, water, and two tribunated ions [sodium and nitrate stay unchanged in solution. P.S. The sodium and nitrate stay unchanged in solution. :cool:
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Siggebo
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[*] posted on 30-7-2012 at 03:47


Sodium hydroxide and ammonium chloride will create ammonia in solution, which you can indeed drive off with gentle heating. Adding the lye might be a bit superfluous though, as ammonium ions react with water to give ammonia as well.

Ordinary ammonia solution will obviously work, probably better.

[Edited on 2012-7-30 by Siggebo]
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franklyn
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[*] posted on 20-10-2012 at 02:12


This is not a timely response but it
does add to the knowledge base.

Mix Lime with Ammonium Sulfate and heat

CaO + (NH4)2SO4 => CaSO4 •H2O + 2 NH3

or else ( better )

Mix dry Hydrated Lime and Urea together and heat

Ca(OH)2 + (NH2)2CO => CaCO3 + 2 NH3

.
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billy666
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[*] posted on 20-10-2012 at 22:21


I've actually done this a few times. In my case, I was synthesizing liquid NH3, very cool reagent btw. Quite dangerous, though. Always perform in a fume hood, or with adequate ventilation.

Anyway, for just my generator part, I used a very dense HDPE container with a bleed off going to a bucket of 5% HCL solution. The generator tube went to an iced drier jar, then to a suckback jar, then to a collection flask immersed in acetone and dry ice.

I collected 3 cups of Ammonium Sulfate and 1.5 cups (approx stoch.) of NaOH finely ground into 2 separate containers.

Then, I placed the Ammonium Sulfate into the HDPE container and added a portion of the NaOH to the container, mixed thoroughly and placed the container onto a hotplate turned to around 100C or so.

Keep adding portions of NaOH until you have generated as much NH3 as needed.

The idea here is that the byproduct is Sodium Sulfate, a moderate desiccant, and it absorbs the H20 from the reaction. The heat is to initiate reaction. This is a slow process, but, if you have the suckback apparatus in place and adequate drying, you can produce a large amount of Anhydrous NH3 with little difficulty.

The setup takes some time, a lot of it, but it's well worth it. Also, I placed valves on both hoses coming out of the generator. I found these invaluable since I was able to quickly stop generation and fall over to the HCL bucket, etc. They provide a lot of control over this monster.

Somewhere I made a lengthy post with diagrams, etc, but, it's been so long now...

Be safe with this one. No danger of explosion, well, NH3 I guess is flammable, but, the danger is from the incredible strength of raw anhydrous NH3, it's very potent stuff.



[Edited on 21-10-2012 by billy666]
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kuro96inlaila
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[*] posted on 24-10-2012 at 04:27


Quote: Originally posted by Rogeryermaw  
or you could try ammonium carbonate available anywhere as "baker's ammonia". it releases ammonia gas and carbon dioxide gas upon heating. no mixing of chemicals required.


let say we heat ammonium carbonate and bubbled the ammonia gas and carbon dioxide gas produced into water.Will it react into ammonium carbonate back in the water?

[Edited on 24-10-2012 by kuro96inlaila]




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AJKOER
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[*] posted on 24-10-2012 at 07:07


To produce pure NH3, just heat store brought aqueous ammonia. Adding NaCl may further decrease the solubility to liberate NH3 at a lower temperature.

However, this does not form dry ammonia gas. Also, one cannot use CaCl2 to dry ammonia as it forms abducts (CaCl2.xNH3).


[Edited on 24-10-2012 by AJKOER]
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