Is it possible for me at home to react atmospheric $\ce{CO2}$ with sodium carbonate to make sodium bicarbonate.
I am seeing if I can take $\ce{CO2}$ out of the air.
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1 Answer
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A process commonly used to teach $\ce{CO2}$ scrubbing to chemical engineering students involves not sodium bicarbonate, but sodium hydroxide ($\ce{NaOH}$).
The reaction is exothermic and is as follows:
$$\ce{CO2 (g) + 2 NaOH (aq) -> Na2CO3 (aq) + H2O (l)}$$
The aqueous sodium carbonate is subsequently treated with calcium hydroxide to precipitate out calcium carbonate:
$$\ce{Na2CO3 (aq) + Ca(OH)2 -> 2NaOH (aq) + CaCO3 (s)}$$
Disclaimer:
This is usually done with much higher concentrations of $\ce{CO2}$ (e.g. >10%) than you would find in the atmosphere (~400 ppm). The point of scrubbing in a chemical plant is to reduce emissions to a level that is still much higher than atmospheric $\ce{CO2}$ levels but lower than governmental standards. I suspect that you would not see a noticeable change in ambient $\ce{CO2}$ levels from putting something like this in a place with such (relatively) low $\ce{CO2}$ to begin with. There is a very low driving force to push gaseous $\ce{CO2}$ into the liquid and solvate it when the partial pressure of $\ce{CO2}$ is low.
There exists a unique relationship between the partial pressure of $\ce{CO2}$ above a solution, the dissolved carbon in the solution, and the pH of the solution, shown here (own work):
Note that the equations on the right-hand side are in solution.
So if you wanted to see what was going on in a controlled environment with no other species in the solution / that could enter the solution, you could just use a pH probe to see how much carbon was pushed into the solution!
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$\begingroup$ I am also trying to get the carbon dioxide out of the scrubber as well. $\endgroup$– CatprogJan 31, 2017 at 1:12
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1$\begingroup$ @Catprog see my edit, I expanded on my answer $\endgroup$ Jan 31, 2017 at 1:13
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1$\begingroup$ @Catprog added some more info. The CO2 needs to enter the solution first, and this is very favorable w/ NaOH (aq). This could then be precipitated out with, as you say, Ca(OH)2 (s). But a direct reaction involves a solid and a gas, and will likely be slower/achieve a lower conversion as a result (also the reaction you suggest is not possible, try balancing it to see why). $\endgroup$ Jan 31, 2017 at 5:55
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$\begingroup$ en.wikipedia.org/wiki/Limewater#Chemistry (I forgot the other part of the reaction) $\endgroup$– CatprogJan 31, 2017 at 22:27