A solute with a partition coefficient of 7.4 is extracted from 25 mL of water into toluene.
a) What volume of toluene is required to recover 99% of the solute in a single extraction?
b) What total volume of toluene is required to recover 99% of the solute in four extractions?
a) Assuming that the solute has only chemical form in each
phase
KD = D =7.4
To extract 99% of the solute (qaq) 1=
0.01
Vorg = [Vaq - (qaq)1 *
Vaq ] / (qaq)1 * D = [25 -
0.01*25] / 0.01*7.4 = 334.45945 mL
Therefore 334.5 mL of toluene is required to recover 99% of the
solute in single extraction
b) ( Qaq)n = ( Vaq /
DVorg + Vaq )n
n=4 ; ( Qaq)4 =
0.01
0.01 = ( 25 / 7.4* Vorg + 25)4
(0.01)1/4 = 25 / 7.4Vorg +
25
7.4Vorg + 25 = 25 / 0.3162277
7.4Vorg +25 = 79.0569415
Vorg = 54.0569415 / 7.4 = 7.304992 mL
Therefore 7.305 mL of toluene is required to recover
99% of the solute in four extractions
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