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Author Topic: azeotrope question  (Read 999 times)

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hefeweizen

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azeotrope question
« on: December 23, 2016, 12:37:10 PM »

I am confused about azeotropes. They are mixtures that cannot change in composition no matter how much distillation you do. A positive azeotrope is one where the boiling point is lower than that of both components in a mixture. A good example is 95.63% ethanol and 4.37% water. This happens because in a positive azeotrope containing X and Y, X and X tend to be together and Y and Y tend to be together.



If X and X tend to be together and Y and Y tend to be together, then why is it that in ethanol and water mixture, you cannot get a more pure ethanol?
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AWK

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Re: azeotrope question
« Reply #1 on: December 23, 2016, 01:45:04 PM »

Quote
They are mixtures that cannot change in composition no matter how much distillation you do
This statement is true only at constant pressure.
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Enthalpy

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Re: azeotrope question
« Reply #2 on: December 25, 2016, 06:50:08 AM »

[...] If X and X tend to be together and Y and Y tend to be together, then why [no separation...]

The ambient heat mixes molecules even in the case where, to some degree, each fits better with identical ones. For instance water and glycerine mix well but produce cold.

In the case of distillation, it's a matter of partial vapour pressure.
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hefeweizen

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Re: azeotrope question
« Reply #3 on: January 07, 2017, 06:24:18 PM »

[...] If X and X tend to be together and Y and Y tend to be together, then why [no separation...]

The ambient heat mixes molecules even in the case where, to some degree, each fits better with identical ones. For instance water and glycerine mix well but produce cold.

In the case of distillation, it's a matter of partial vapour pressure.

Thanks! Do you mind explaining more?  How does heat mix molecules?
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shiffdaddy

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Re: azeotrope question
« Reply #4 on: January 24, 2017, 03:44:00 PM »

Heat is the movement of particles right?  So wouldn't it make sense that this movement of particles causes some sort of mixing
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