How to purify a carboxylic acid by recrystallisation?

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makami11
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The method for purifying an organic liquid like ethanoic acid is straightforward as it's already a liquid. But what if you hydrolyse an ester to form the carboxylic acid salt and ethanol. I'm not sure how you would purify the salt to just get ethanoic acid on its own through recrystallisation as a solid crystal?
Please help!!
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revisionlad
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Hey...
I don't think we have to know it for our spec but in the reaction all we have to know is to heat and reflux slowly to obtain the C.Acid and alcohol. (Heat and reflux when we acid-catalysed hydrolise it).

I found this link if it might help understanding why it maybe difficult to purify; https://www.thestudentroom.co.uk/sho....php?t=4212189

However, you are speaking about base catalysed hydrolysis where the carboxylate salt is formed.


Hence, can we just not liberate it w/dilute mineral acid to obtain the C.Acid but not in crystalline form?
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makami11
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ahh are you doing AQA too? In the spec it does say under carboxylic acids ( Students can identify an ester by measuring its boiling point, followed by hydrolysis to form the carboxylic acid which is purified by recrystallisation, and determine its melting point)
Yeh liberating the c.acid with a dilute acid does make sense, but I was't sure cause I assumed the spec meant base hydrolysis.
There may be another method cause to determine melting points, it has to be a crystal c.acid from recrystallisation first?
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