Ethanol - salt precipitation


by jsmith613
Tags: ethanol, precipitation, salt
jsmith613
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#1
Mar11-12, 04:45 AM
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1. The problem statement, all variables and given/known data


what is the purpose of adding ethanol in step 5 in the following description?

http://www.creative-chemistry.org.uk...s/N-ch5-08.pdf
2. Relevant equations


3. The attempt at a solution
Does adding ethanol make the liquid phase (which is now a homogenous mixture) less polar because ethanol is slighly hydrophobic hence the salt is less soluble so precipitates out?
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Borek
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Mar11-12, 05:50 AM
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Link is broken.

But your explanation is more or less what could be expected.
jsmith613
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Mar11-12, 06:10 AM
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Quote Quote by Borek View Post
Link is broken.

But your explanation is more or less what could be expected.
http://www.creative-chemistry.org.uk...s/N-ch5-08.pdf

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Mar11-12, 06:29 AM
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Ethanol - salt precipitation


I don't think calling ethanol hydrophobic is the best approach. It has a lower dielectric constant and because of its size it is not as effective at solvation, so it doesn't isolate ions as effectively as water does.
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Mar11-12, 07:15 AM
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Quote Quote by Borek View Post
I don't think calling ethanol hydrophobic is the best approach. It has a lower dielectric constant and because of its size it is not as effective at solvation, so it doesn't isolate ions as effectively as water does.
would it please be possible then to give me an A2 level answer (i don't know about dielectric constant) that would gain 1 or 2 marks?

thanks
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Mar11-12, 12:12 PM
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Quote Quote by Borek View Post
I don't think calling ethanol hydrophobic is the best approach. It has a lower dielectric constant and because of its size it is not as effective at solvation, so it doesn't isolate ions as effectively as water does.
would the following be better:

"the homogeneous mixture of ethanol and water is less polar that water alone so the salt is less soluble and hence precipitates out
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Mar11-12, 12:27 PM
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Quote Quote by jsmith613 View Post
the homogeneous mixture of ethanol and water is less polar that water alone so the salt is less soluble and hence precipitates out
Sounds good to me.


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