Ask A Scientist© Chemistry Archive

name         David C.
status       other
age          20s

Question -   Despite consulting a variety of sources, I do not yet
have a satisfactory explanation as to why carbon dioxide is more soluble
in cold water than it is in warm water.
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David,

Any water soluble gas becomes more soluble as temperature decreases because,
in and of themselves, gas molecules have little affinity for each other --
after all, that is why they are gases. When dissolved in water, CO2 forms weak
bonds with the water molecules. The lower the temperature, the stronger the
bonds, the greater the amount of CO2 that can be dissolved.

Regards,
ProfHoff 301
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David C.,

Your question goes back to Le Chatelier's Principle in
chemistry. Without going into the gory details, the
principle gives us the fact that a dissolved gas (carbon
dioxide in this case) always becomes less soluble with
increasing temperature. One can testify to this from
experience that much more gas is released from a can of
soda that is opened when it is warm rather than when it
is cold. This illustrates that temperature affects the
solubility of a gas.
I hope that this answers your question.


Sincerely,

Bob Trach
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All gases are  more soluble in cold water than in warmer water. This is a
general trend. The reason has to do with the thermodynamics of the reaction:
GAS(in solution) = GAS(gas phase)

The entropy change, delta S, of this reaction is always positive because the
gas molecules are less constrained than the gas molecules in solution. The
change in Free energy of reaction with an increase in temperature is the
negative of delta S. The bottom line is that the solubility of gases
decreases with increasing temperature.

This effect is particularly large for gases like CO2 that undergo specific
reactions with water. Ammonia would be another example.

Refer to  the website: http://www.chem.uidaho.edu/~honors/gassol.html

Vince Calder
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