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H20, CO2 and O2 in a Closed Container for a Long Time

  1. Mar 15, 2014 #1
    How much oxygen would make it's way down to the water if no mixing happens when put into container? I always hear of blanket of CO2 over a liquid. I'm trying to relearn some thermodynamics principles. Would the partial pressure between the CO2 never allow the oxygen diffuse into the water if the height of CO2 is say 3" high over a 12" diameter of liquid? I tried doing some googling but get lots of hits from lungs and respiratory due to Fick :-) I'd like to relearn the processes that allows or inhibits the oxygen getting to the CO2 which then leads to the liquid. Would all three be completely separate in another 1000 years I guess? Thanks for any help.
     
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  3. Mar 15, 2014 #2

    Vanadium 50

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    You clearly have some system in mind. But we don't know what it is. Can you describe the thing you are thinking of?
     
  4. Mar 15, 2014 #3
    Mixing or not, eventually, the CO2 and O2 will interdiffuse and form a uniform gas mixture. Also, water vapor will evaporate into the gas mixture until its partial pressure is equal to the equilibrium partial pressure at the system temperature (assuming that only small amounts of CO2 and O2 dissolve in the liquid water). Some of the CO2 and O2 will dissolve into the liquid water until their concentrations in the liquid are in equilibrium with their partial pressures in the overlying gas mixture. So eventually, the partial pressures of all three components in the gas phase will be in equilibrium with the concentrations of these three components in the liquid phase. This will all take place on a time scale of minutes to hours, not thousands of years.

    Chet
     
  5. Mar 15, 2014 #4
    First of all want to apologize because I think this should be in the homework Section. The system would be a large glass bottle with an air tight seal. I found a similar question in this same forum. It was about wine making. I always thought the co2 blanket wouldnt allow the oxygen to diffuse to the water. I figured the oxygen and co2 wouldnt mix therefore being negligible to mix with said water. I could see evaporation and condensation due to small variations in temp and pressure allowing o2 to mix with the condensation falling and penetrating the co2 layer. Maybe my understanding is wrong but to make the question simple: if I had a mixture of co2 and o2 they would never mix into equilibrium. That eventually co2 would be on the bottom and o2 on top.
     
    Last edited: Mar 15, 2014
  6. Mar 15, 2014 #5
    Thanks Chet. You beat my slow phone txting response. So what is the thermodynamic term of o2 and co2 combining into a mixture instead of separate layers? Im guessing kinetic energy and partial pressure are at play. Its been too many years since I was good at these things.
     
  7. Mar 15, 2014 #6
    It's diffusion, which is driven by differences in partial pressure (concentration) between the two regions and related to kinetic energy jostling the molecules so that they intermingle.

    Chet
     
  8. Mar 15, 2014 #7

    Vanadium 50

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    Please repost it there, then, using the template. Also, please be clear about the system you are describing.
     
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