Sciencemadness Discussion Board

What Gas Was Produced?

okelly4408 - 2-3-2013 at 12:24

Hello,
Recently I made a small amount of sodium nitrate by reacting sodium hydroxide and ammonium nitrate. After desiccating the solution and recrystalizing the sodium nitrate I dissolved it in a bit of water. To this water I then added sodium bisulfate. When this was added it started to violently effervescence. I am clueless in determining what this gas was. Any help is appreciated, thanks!

woelen - 2-3-2013 at 12:35

This gas must be carbon dioxide. Probably you added excess NaOH, which leaves a solution of NaOH and NaNO3 (and NH3). After evaporation, NaOH and NaNO3 remain, but the NaOH absorbs CO2 from the air and at the time when all is dry, all of it will have been converted to Na2CO3. The acid NaHSO4 is strong enough to release CO2 from Na2CO3.

blogfast25 - 2-3-2013 at 12:45

Recrystallise your product: NaNO3 and NaOH/Na2CO3 are fairly easy to separate that way (look uo their solubilities). Next time, try working nearer to stoichiometric conditions.

okelly4408 - 2-3-2013 at 14:05

Quote: Originally posted by woelen  
This gas must be carbon dioxide. Probably you added excess NaOH, which leaves a solution of NaOH and NaNO3 (and NH3). After evaporation, NaOH and NaNO3 remain, but the NaOH absorbs CO2 from the air and at the time when all is dry, all of it will have been converted to Na2CO3. The acid NaHSO4 is strong enough to release CO2 from Na2CO3.

Ah ok that makes sense. I did have the hydroxide in slight excess but I did not know that it could form sodium carbonate.. Thanks for the help though.