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Alcohol in beer would evaporate extremely slowly in cold temperatures?

  1. Sep 11, 2013 #1
    I'm guessing the alcohol in beer would evaporate extremely slowly in cold temperatures like a fridge. I hear a lot of people say otherwise, so I'm wondering if it even evaporates a noticeable amount in 24 hours?
     
  2. jcsd
  3. Sep 11, 2013 #2
    It depends on the conditions inside the fridge.

    If the fridge is airtight, then the worst-case scenario is that equilibrium is achieved and the entire fridge becomes filled to saturation with ethanol vapors. The vapor pressure of ethanol at 4°C is about 0.02 atmospheres, so if the interior of the fridge has a volume of 1 cubic meter, the amount of ethanol vapor at equilibrium is PV/RT = 0.9 mol, or 40 g. So it is theoretically possible that you could lose all the ethanol as long as your beer has less than 40 g of ethanol in it (probably the case unless you have put a lot of beer in the fridge).

    But that is the worst-case scenario, and it will take a long time to achieve equilibrium unless you have dispersed the beer into an aerosol.

    I would guess, roughly, that the concentration would not be noticeably changed after 24 hours, but probably would be after a week. Here is an example of a similar (informal) experiment. Of course, you could prevent even this by simply covering the beer.
     
  4. Sep 11, 2013 #3

    SteamKing

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    Is that why it's hard to keep beer in a refrigerator? People drink it up before it evaporates?
     
  5. Sep 12, 2013 #4

    Borek

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    Who keeps their beer opened?
     
  6. Sep 12, 2013 #5

    SteamKing

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    Well, in case the alcohol might evaporate thru the can, you want to drink it ASAP.
     
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