Ask A Scientist Chemistry Archive

name         Tom D.
status       student
age          15

Question -   Can you tell me how much CO2 can be dissolved in water ?
Is there another form of carbon that can have a higher concentration in
water?  CO or something else?
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This is a far more difficult question than it appears at first glance. The
solubility of CO2 in water depends upon several factors: 1. The pressure of
CO2 in equilibrium with the solution. Solubility increases with increasing
pressure. 2. The temperature. Solubility decreases with increasing
temperature. 3. The pH. The solubility of CO2 increases with increasing pH.
4. The presence of other substances. The solubility tends to decrease with
concentration of "inert" ionic solutes like sodium chloride, but may
increase or decrease with increasing concentration of organic compounds,
depending upon the compound. You can find out "pieces" of the answer if you
do a web search, but I do not know of a single reference that tabulates all
the variables in one place. In general sodium and potassium carbonate or
hydrogen carbonate salts will be more soluble than gaseous CO2 alone.
 
Vince Calder
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CO2 solubility depends in part on conditions such as temperature and
pressure of the water among other things.

It is not clear what you want when you ask about another form of carbon that
can have a higher concentration dissolved in water- in terms of total atoms
of carbon, or total molecules?   For example for many of the alcohols you
can essentially add alcohol continuously until the mix approaches 100%
alcohol (becoming essentially water dissolved in alcohol)

If it must be an inorganic form of carbon then generally the carbonate
salts will generally have much higher concentrations than plain CO2 at
atmospheric pressure.  For example the solubility of sodium carbonate is
455 g/L or about 4 moles/L, which is much higher than the solubility of CO2
at 1 atmosphere (about 0.03 moles/L).

Don Yee
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I am not sure what the maximum concentration of CO2 in water is.  If you
want a high carbon concentration in liquid form use methanol or some
other alcohol.  If it really needs to be in the presence of water, add a
drop of water...

Greg Bradburn
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