Problems
(1) Compound X has a distribution ratio of 2.7 for benzene/water. For an aqueous sample containing 4.5
mg of X per 50 cm^3 , calculate:
(a) the volume of benzene required to remove 99.0% of X with a single extraction, and(b) the number of extractions with 50 cm^3 of benzene required to remove 99.0% of X.(2) A 100 cm^3 volume of 6 M HCl contains 0.200 g of SbCl 5 for which the distribution ratio into diethyl
ether is 4.25. If 25 cm^3 of ether is used for each extraction, how many are required to remove (a) 99.0%
and (b) 99.9% of the SbCl 5 from the acid solution?
(3) Acetylacetone (AcAc) is a chelating agent for many metals. 50 cm^3 of an aqueous solution of M2+ (5
× 10 –^3 M) is equilibrated with 20 cm^3 of ether containing an excess of AcAc. If 94% of M is extracted
into the ether, calculate the value of the distribution ratio given that M2+ + 2AcAc– → M (AcAc) 2 is the
only reaction.
(4) Use the following data to estimate the distribution coefficient, KD, and the acid dissociation constant,
Ka, for trifluoroacetylacetone distributed between water and chloroform:
log 10 D 0.3010 0.3010 0.3010 0.1461 –0.0458 –0.3979 –0.6989
pH 1.16 2.09 3.25 6.29 6.68 7.40 8.00(5) The following data relate to the distribution of 8-hydroxyquinoline (HOx) between chloroform and
water:
Calculate the distribution ratios and the concentrations of HOx remaining in the aqueous phase after
equilibration of 0.1% aqueous solutions at pH values of 1, 6 and 10 with equal volumes of chloroform.
(6) Indium, cadmium and silver can be extracted into chloroform as their 8-hydroxyquinoline
complexes, and the pH1/2 values for these metals are 2.1, 6.3 and 8.8 respectively. Plot a graph of
theoretical percent extraction against pH over the range 0 to 9 for each metal. Deduce the pH of
incipient extraction (0.01%) and complete extraction (99.99%) for each metal, and comment on the
feasibility of separating each from the other assuming that all the distribution coefficients are
sufficiently high.
(7) A GC column packed with a non-polar stationary phase gave the following retention times for a
series of hydrocarbons:
Compound t'R (min)methane and air 1.8ethane 2.4