Alchohol in low atmospheric pressure/vacuum

Discussion in 'Chemistry' started by domesticated om, Jul 16, 2007.

  1. Nasor Valued Senior Member

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    Look, I've tried to be nice here, but you keep insisting that you’re right when it's clear that you have absolutely no f***ing idea what you're talking about. Read a basic chemistry textbook.

    The vapor pressure of a liquid increases as temperature increases. If the vapor pressure of a liquid is greater than the atmospheric pressure around the liquid, that liquid will boil. That's why you have to heat water to boil it - you are heating it to raise its vapor pressure. If the atmospheric pressure is lower, then you don't have to heat the liquid as much to get it to boil because it doesn't have to attain as high a vapor pressure in order to start boiling. If you increase the atmospheric pressure on a liquid to above 1 atm, you now have to heat the liquid above 100 C to get it to boil. If you take a pot of water to the top of a high mountain, it will boil at less than 100 C because the pressure is lower. I don't know how I could make this any more explicit.
     
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  3. Chatha big brown was screwed up Registered Senior Member

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    I went to some web sites and many seem to say a low pressure equals low boiling point and high pressure equals high boiling point. Sorry for the confusion guys. I think I was equating vapor point with boiling point or something like that.
     
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  5. Chatha big brown was screwed up Registered Senior Member

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    Okay guys, I was on my way to work when I deciphered the root of our confusion. I am a chemistry undergrade and as a chemistry undergrade you get to work with a lot of standardization or STP's, and the STP of water is 100 degees at 1 atm. You get used to working with STP's so much that you use them all the time. The confusion is that I was using boiling point in relation to STP. I knew water boiled at lower temperatures at high elevation, which is why I said "increase the boiling point", but what I meant to say is that the water at high elevation will "need to increase its boiling point towards STP". It seems I was kind of thinking too far ahead each time, and I was further confused when you guys tried to correct me, which I mistakenly saw as a false arguement. Basicaly, all you need to know is that I was working towards or from STP. My mistake.

    So as far as alchohol is concerned, alchohol will have a lower boiling point in a system of low pressure, alchohol is already very volatile so it most likely will disappear in low pressure.
     
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  7. Nasor Valued Senior Member

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    Try zero degrees.
     
  8. Read-Only Valued Senior Member

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    One more minor correction right here. As to the statement above, there was NO "our confusion" - only yours.
     
  9. Chatha big brown was screwed up Registered Senior Member

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    I guess the only thing to say is ....oopsy daisy!

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  10. Chatha big brown was screwed up Registered Senior Member

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    Actually, I was talking about the normal boiling point of water. In Chemistry, the normal boiling point of water is the boiling point at 1 atm, which is 100 degrees celcius or 373k. But you should probably look it up in any text book (look up the "normal boiling point" of water) cause a lot of this stuff is too elementary that it sometimes confuses me.
     
    Last edited: Jul 31, 2007
  11. Omnignost Registered Senior Member

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    It is a bit scary that there actually is a discussion about this. What happens when you take a flask of ethanol (use a round bottom flask or it may break) and attach it to a vacuum pump is that the ethanol starts to boil and the flask gets really cold on the outside. Pretty soon frost forms on the outside and boiling stops. Afrter a while the alcohol has evaporated. We professionals usually do this on a rotary evaporator where we rotate the flask slowly while putting it in a bath of warm water.
     
  12. Read-Only Valued Senior Member

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    Quite true and something quite commonly done to recover a substance that was dissolved in the ethanol.

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    It just seems that once in a while we encounter someone here who has his head wired backwards. That wouldn't necessarily be bad except the often become adamant about it - despite several people (including a few of us that are professionals) giving detailed explanations and examples to the contrary. It often becomes disheartening and sometime downright disgusting trying to get simple things through to them. (One chemistry or physics class in high school and they become immediate experts! Ugh!!!)
     
  13. leopold Valued Senior Member

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    liar, or you would have never made the ridiculous claims in this thread.
     
  14. Chatha big brown was screwed up Registered Senior Member

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    Well, I never claimed to be an expert, and I am sure you don't even have to take college level chem to figure out this discussion. A lot of times I may become adamant over virtually anything, thanks partly due to endless arguements with people I know who get me mad(don't ask). As for whether or not i'm a chem major, that doesn't even really matter, unless you want to personally email me so I can give you my school ID so you can enquire an enrolment verification...blah! blah! blah!. Maybe you may also want to check my Business degree. For any info, i''m taking 300 level chem courses. Yes, some people here on sciforums can be annoying, thats a given. Some of these people make mistakes- not everybody truely enjoys intellectual discussions by typing over and into the internet. But some professionals here too can be annoying, they can't explain anything to save their life. A mentor of mine told me something that I would never forget, he said "how much you know about something is a function of how well you can teach it to anybody". That is the only fault I see from professionals here, but its probably because of the interface-internet forum. I make mistakes; big, small, medium, you name it. But even worse than me making mistakes is the fact that I may become adamant, which is a character I picked up but have totally stoped. Have the time I post on this forums, I'm either working or going to work, but almost always distracted, though that shouldn't be an excuse. Cheers
     

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