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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: mana on March 01, 2018, 03:54:35 PM

Title: Partition coefficient in extraction problems
Post by: mana on March 01, 2018, 03:54:35 PM
hi all
I have solved 4gr butanoic acid in 100 ml water and I want to extract it with 100 ml benzene. the distribution constant (k) btw benzene and water is 3. I want to calculate the residual  butanoic acid remained in water after 3rd extraction with benzen.
I don't know in the formula for calculation residual extract, do I have to substitute 3 for k or 1/3 (because I'm calculating residual butanoic acid in water not in benzene)?
can anyone help :-\
and the formula is wn= w0(kv/kv+s/n)n
wn: the residual butanoic acid in water after n times extarction
w0: the amount of butanoic acid in water at first (4gr)
v: volume of water
s: volume of benzene
Title: Re: Partition coefficient in extraction problems
Post by: Borek on March 01, 2018, 06:10:04 PM
Don't make things more complicated than they are, calculate how much was extracted and subtract from the initial.
Title: Re: Partition coefficient in extraction problems
Post by: mana on March 01, 2018, 10:23:36 PM
Quote from: Borek on March 01, 2018, 06:10:04 PM
Don't make things more complicated than they are, calculate how much was extracted and subtract from the initial.
yes, you are right but I want to know how to calculate with formula too,  ???
Title: Re: Partition coefficient in extraction problems
Post by: Borek on March 02, 2018, 02:52:46 AM
If you don't know how to follow the formula try to calculate the changes on the step by step basis - in each step you have known initial concentrations and initial volumes, that (and the fact total amount of the butanoic acid doesn't change) allows you to easily calculate final concentration ratio.