suppose solute A has a partition coefficient of 4.0 between diethyl ether and water. Demonstrate that if 100mL of solution of 5.0g of A in water were extracted with two 25mL portion of diethyl ether, a smaller amount of A would remain in the water than if the solution were extracted with one 50mL portion of diethyl ether.

Answer 1

K_o/a = (organic)/(aqueous)
o = organic
a = aqueous
5/100 = aqueous phase to start.
Let x = g in organic phase in 25 mL ether; then (x/25) = concn in organic phase and
(5-x)/100 = the amount left in the water phase.
4.0 = (x/25)/(5-x)/100
x will give you the amount in the organic phase, evaluate 5-x to determine the amount left in the water, then do the extraction again (on paper) to find the final concn in the water phase. Then redo with the different numbers for the single extraction. Compare. Two extractions with a smaller amount of solvent(25 each time) is more effective than a single extraction with 50 mL.
Post your owrk if you get stuck.

Answer 2

Where Did the 4.0 come from?

Answer 3

3. 4.0 = (x/25)/(5-x)/100
x= -1/3
16/3 left in the water