Please help! HCO3-/CO2 equilibrium!!

[acuriousperson]

Hi,
I am doing a science fair project where the CO2 concentration in the air has to be maintained. I was planning on doing this by adding a certain concentration of HCO3- to the water in an airtight container so that I could control the atmospheric CO2 because I know that an equilibrium will be established between the air and the water.
Does anyone know the formula for equilibrium? I'm trying to get the atmospheric concentration of CO2 to be 580 ppm. What HCO3- concentration should the water have?
Help would be greatly appreciated!
Thank you!

[deleted-71417]

Hi,

You pose a question easily stated, but not so easy to answer. Here is a Wikipedia article on Carbonic Acid that has some good background:

http://en.wikipedia.org/wiki/Carbonic_acid

Here is a site that provides a downloadable software program with explanations that may be useful:

http://cdiac.ornl.gov/oceans/co2rprt.html

Unfortuanately you will have to do some careful conversion of your input data to their units of measurement to get anywhere with it.

I am sorry not to be able to give you a simple answer, but the answer is complicated to figure out and requires a rather precise knowledge of the composition of the water solution and the temperature of the system, and even then I am unsure how accurate the pH determination will be.

Best of luck deciphering all this!

Have fun with the project! You may want to search google for alternative solutions to your problem. I came across several sites that discussed regulating CO2 concentrations in aquariums by direct injection of CO2 into the water to keep plants and fish happy. The problem is they are all rather expensive, and I suspect they are trying to keep concentrations much lower than you asked for.

Best regards,

Barrett Tomlinson

[deleted-71588]

It would help if you could provide some additional information on your experiment. Maintaining a 580 ppm of CO2 in a small enclosed container without some feedback control system may not be possible. If we know more about what you are actually trying to experiment with, we maybe able to recommend a different approach where maintaining a specific CO2 level is not required to do your experiment.