marnieeee
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Report Thread starter 8 months ago
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im trying an exam question at the moment, and it says this: Two students were each given a different alcohol. They each added their alcohol to water in a
separating funnel, shook the mixture and then left it to stand.
The diagrams show the results.
"diagram of one separated and one not"

What can be deduced about the alcohols given to each student? You should explain why the alcohols behave differently in this experiment.

Anyone have any ideas as to what sort of answer they're looking for?
Thanks x
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charco
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(Original post by marnieeee)
im trying an exam question at the moment, and it says this: Two students were each given a different alcohol. They each added their alcohol to water in a
separating funnel, shook the mixture and then left it to stand.
The diagrams show the results.
"diagram of one separated and one not"

What can be deduced about the alcohols given to each student? You should explain why the alcohols behave differently in this experiment.

Anyone have any ideas as to what sort of answer they're looking for?
Thanks x
If the liquids separate into two layers what does it mean?
If they don't - why don't they?

What causes the behaviour above?
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username5064508
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My best guess is that:

The alcohol which mixes with water does so because both water and the alcohol have polar O-H groups, making the molecules polar. This allows the alcohol to dissolve in water, as polar solvents (water) can only dissolve polar solutes (alcohol).

The alcohol which separates out is likely to be a longer-chain alcohol, as solubility decreases with chain length due to more and greater intermolecular forces between alcohol chains. It still has the polar groups, but increased chain length limits solubility.

Therefore, the alcohol which separates is likely to be longer chain compared to the alcohol which does not separate out.
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marnieeee
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(Original post by charco)
If the liquids separate into two layers what does it mean?
If they don't - why don't they?

What causes the behaviour above?
okay thank you for your help
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marnieeee
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(Original post by HRobson_BMC)
My best guess is that:

The alcohol which mixes with water does so because both water and the alcohol have polar O-H groups, making the molecules polar. This allows the alcohol to dissolve in water, as polar solvents (water) can only dissolve polar solutes (alcohol).

The alcohol which separates out is likely to be a longer-chain alcohol, as solubility decreases with chain length due to more and greater intermolecular forces between alcohol chains. It still has the polar groups, but increased chain length limits solubility.

Therefore, the alcohol which separates is likely to be longer chain compared to the alcohol which does not separate out.
ahhh i understand now, thank you!
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