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Thread: What does ethanol evaporate into?

  1. #1 What does ethanol evaporate into? 
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    Ethylene? And while it is in its gaseous form can it condense? I was thinking of building a co2 generator for my aquarium plants using only yeast and sugar but am worried about the evaporated ethanol to get into the tank.


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  3. #2  
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    Ethanol is ethyl alcohol. You know, grain alcohol, booze, drinking alcohol.
    It evaporates into the air.
    It is unlikely you would generate enough alcohol to worry about from a small fermentation.


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    So that means when ethanol is evaporated into the air, they still remain as C2H5OH without the H2O taken from them?
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  5. #4  
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    Quote Originally Posted by molecool View Post
    Ethylene? And while it is in its gaseous form can it condense? I was thinking of building a co2 generator for my aquarium plants using only yeast and sugar but am worried about the evaporated ethanol to get into the tank.
    Now you're being silly. Evaporation does not involve one substance changing into another. If that happens when something is heated, we call decomposition. Ethanol liquid evaporates into ethanol vapour.

    Now, you can "deydrate" ethanol into ethylene, using a suitable catalyst: CH3CH2OH -> CH2=CH2 + H2O.

    See here for the conditions: dehydration of ethanol to give ethene

    Obviously you are not going to get this in your "digester".

    At 35C, ethanol has a vapour pressure of 100mmHg, so about 1/8 of an atmosphere. And at 20C it is about 40mmHg, about a 20th of an atmosphere. So I doubt you will get a lot of carryover of vapour with the CO2. If you do, you can tell us all what fish are like when they are pissed.
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    LOL, now I get it. Basically this also applies to everything that evaporates too, right?
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  7. #6  
    KJW
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    It's worth remarking that if one has an open beaker of ethanol and an open beaker of water side by side inside a not too large closed container, then the ethanol will transfer itself to the beaker of water.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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  8. #7  
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    Quote Originally Posted by KJW View Post
    It's worth remarking that if one has an open beaker of ethanol and an open beaker of water side by side inside a not too large closed container, then the ethanol will transfer itself to the beaker of water.
    Wow, why is that?
    dan hunter likes this.
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  9. #8  
    KJW
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    Quote Originally Posted by molecool View Post
    Quote Originally Posted by KJW View Post
    It's worth remarking that if one has an open beaker of ethanol and an open beaker of water side by side inside a not too large closed container, then the ethanol will transfer itself to the beaker of water.
    Wow, why is that?
    Without the open beaker of water, the open beaker of ethanol would maintain an equilibrium partial pressure of ethanol vapour in the closed container. But with the open beaker of water present, the ethanol vapour will become absorbed by the water. This decreases the partial pressure of the ethanol vapour which the open beaker of ethanol tries to maintain by evaporating. But the water continues to absorb the ethanol vapour, thus preventing the equilibrium partial pressure of the ethanol vapour from being maintained. The overall result is a transfer of ethanol to the water. Some water will also transfer to the ethanol, but because the ethanol is more volatile, the transfer of the ethanol to the water will predominate.

    Thermodynamically, the mixture of ethanol in water has a higher entropy than the two separate liquids, and this drives the process.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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