When left out in an open container, what % abv does vodka retain at room temperature?
If I pour vodka (40% abv) into an open glass, and then leave it out overnight (or for some time), what percent ABV does it stabalize at? Or does all of its alcohol content evaporate (leaving just barley-water in its wake)?
Also, as a followup, does the same behavior apply to other alcohols, like whiskey? And finally, at what rate roughly does vodka lose ABV at room temperature?
(3)3 Comments
Sorted by latest first Latest Oldest Best
The answer given by another commenter, that unless the room is able to reach an equilibrium concentration of ethanol, all ethanol will evaporate from the glass, without stopping at any specific point, is absolutely correct. (Specifically, at atmospheric pressure and 20 degrees celsius, this would be around 5.8% ethanol in the atmosphere--and I think you'd probably notice if the air you're breathing was 5.8% alcohol)
However, as someone who googled this exact question out of curiosity after downing a glass of vodka that had been left out for several days and is currently feeling rather tipsy, I can personally attest to the fact that this is not the complete story. You see, the equilibrium state (i.e. the state that this system will naturally tend to approach over time) is a state where all the ethanol has evaporated from your glass. However, this tells us absolutely nothing of the rate at which this will happen. You see, as the concentration of ethanol decreases, the rate of evaporation will decrease as well. I'll admit that I'm not knowledgeable enough about chemistry (my background is in chemical engineering) to provide any hard numbers about how the rate will decrease, but intuitively speaking it should be rather obvious that it would. After all, if the equilibrium state is for there to be no ethanol in the cup, then surely the farther you are from this state, the greater the thermodynamic driving force will be. Also the rate could be slowed by a number of other factors (as the other commenter mentions), such as the shape of the glass or the pattern of air currents in your room.
Now, as the other commenter mentions, in order to provide any hard numbers about how much ethanol is left in your cup, we would need to know a lot more information (most crucially the time you left it for), but I'd be willing to bet that as long as there's still a significant amount of liquid in the cup there will still be enough alcohol to at least get you tipsy. Just don't expect it to still be at 40%.
As a chemist I'd say that the question is really impossible to answer as given.
The gist is that for a water/ethanol mixture both components will evaporate. So if the liquid is left out long enough, the liquid will evaporate completely.
The atmosphere contains essentially no ethanol so an equilibrium between the whole atmosphere and the ethanol in a glass can never be reached. There is water in the atmosphere (aka humidity) so the evaporation of water could be retarded, or prevented entirely if the "local" humidity is 100%. But unless the "local" humidity is already 100% then an equilibrium between the liquid and the atmospheric water won't be reached either.
Pure ethanol has a higher vapor pressure and thus evaporates faster than pure water (in 0% humidity). So the gist is that as liquid evaporates the water/ethanol composition of the liquid will change. Thus the relative rate of evaporation of water and ethanol changes too.
In terms of the rate of evaporation there are a number of unspecified parameters.
How much volume compared to the exposed surface area? So liquid will evaporate more slowly from a tall narrow glass than a short wide one.
Temperature? The higher the temperature the faster the evaporation.
Air currents? If you use a fan to blow air across the glass evaporation will occur much faster than if a fan isn't used.
No alcohol evaporates at room temperature, so 40% vodka will be 40% in the morning.
Alcohol evaporates at 174 degrees, only cooking can reduce the abv.
Terms of Use Privacy policy Contact About Cancellation policy © freshhoot.com2025 All Rights reserved.