Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: jnimagine on September 29, 2008, 08:53:09 PM
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Hi,
We're doing a lab about distillation.
and I'm very lost as to how to answer this question.
If you're given an unknown which is a mixture of an alchol and small volume of higher boiling impurity. What are some expected results and behaviour of mixture during the simple distillation??
ok... so since we haven't performed the lab yet...and I am not familiar with this topic...
I am sooo lost... :( I know that higher boiling point means less volatile...? and that the vapour phase is always richer than the liquid phase of more volatile compound.
Help please~ > . <
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Start here:
http://www.chem.arizona.edu/~salzmanr/480a/480ants/vpdiag&/vpdiag&.html
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Start here:
http://www.chem.arizona.edu/~salzmanr/480a/480ants/vpdiag&/vpdiag&.html
I read the whole thing.
I do kinda understand the graphs... but a little shaky about positive and negative deviations...
however... about the question about the unknown... i'm not sure what it's trying to get at from saying "mixture of an alcohol with a very small volume of a much higher boiling impurity.".
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One of the substances in your mixture is going to become gas much more easily than the other. Which and why?
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One of the substances in your mixture is going to become gas much more easily than the other. Which and why?
i know that higher boiling point means less volatile...
so i'm alcohol's more volatile so can become gas more easily???
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Yes.
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Yes.
but it says in the question that it's a "small volume" of high boiling "impurity". What are they trying to get at by saying small volume and impurity??? and how would this be shown in simple distillation??
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No idea what they are aiming at, it will be just a distillation - long you will be able to collect just alcohol at relatively constant temperature.
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No idea what they are aiming at, it will be just a distillation - long you will be able to collect just alcohol at relatively constant temperature.
so if we just assume that the impurity is just an ordinary compound that's part of the mixture, what's the expected result and the behaviour of the mixture during this distillation??
What I know is that since the impurity has higher boiling point, it will be less volatile. So the other part of the mixture that is present in a lager volume, would reach the boiling point before the impurity. but this doesn't really answer the question vey well...
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It seems like it does. The more volatile substance boils off first (turns into gas). This allows it to be separated from the impurity.
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It seems like it does. The more volatile substance boils off first (turns into gas). This allows it to be separated from the impurity.
i think it only answers part of the question where it asks you about the expected result..
What would be the behaviour of the mixture during distillation?? It doesn't answer this question....
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hey guys
thanks for all your generous *delete me*
um apparently, regarding the behaviour, I should be looking at things like temperature changes, amount of volume collected, and whether the alcohol is well separated from the impurity...
hmm.... what can I say about these things in this situation??
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don't know why it says *delete me* there....- -;;
anyways.. I'd really appreciate anyone's help on this > . <