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H2O column in vacuum distillation

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SaintJude

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What is the point of a H2O coming out in vacuum distillation? And while I'm at it, is the vacuum source decreasing the pressure of the apparatus?

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And ignore the following image has nothing to do with the question, but I just found it in the medicine post, and love it so I wanted to bookmark it for myself.

http://smashey.files.wordpress.com/2009/11/cr-fig-2.jpg
 

chiddler

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In vacuum distillation, pressure of the system is dropped so that boiling point of liquid decreases.

that said, what do you mean H2O has to come out? it depends on the solution. if there is h2o in it, then it the vacuum may pull it out.

i don't understand the context of your question.

in that image, i don't see any H2O coming out, unless it is in the solution.
 

SaintJude

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Why do they have H2O written in that picture?

Edit: And the point of vacuum source is to prevent pressure from coming to high.
 

chiddler

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i wrote "so that boiling point increases". i meant "decreases".

vacuum is to reduce pressure so that boiling point decreases.

sorry
 

SaintJude

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Yeah, I did but I don't understand how it does that. You just "stick in some water" and suddenly the solution cools? What? Strateego, please illuminate me from your googling adventure.

And also MY google search resulted in this:

Q: How fast should the water run through the condenser?
A continuous flow of water through the condenser is necessary; however, the lower the flow rate, the lower the pressure and the lower the chance of having the tubing pop off (resulting in you spraying yourself or others).
What? I thought, the faster the velociy, the lower the pressure, so you would want a high flow rate since vacuum distillation is all about low pressure system. (If this becomes a MCAT question, I expect a check in the mail please :)
 

chiddler

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it's really easy to see if you've seen it yourself. not so easy to describe via text

it is a pipe with a sleeve around it. the sleeve has water in it so the inner surface of the pipe is always cool. this way, when gas contacts it, it cools down and becomes liquid.
 
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