1000 questions Partition Coefficient

Question 1

The concentration of Iodine in water and trichloromethane was 0.24 and 0.012 mol dm^-3 respectively. Find the partition coefficient between water and trichloromethane.

Question 2

5.0 g of luciferin is shaken in a separating funnel containing 10 mL of water and 50 mlL of ether and was allowed to reach equilibrium. Given that the Kd water to ether is 7.5, calculate the amount of luciferin that has dissolved in the ether.

Question 3

i) If iodine is shaken with 100 cm³ of water and 100 cm³ of an organic solvent, the
concentration of iodine in the water layer is 4.0 x 10^–3 mol dm^–3 and in the organic
solvent is 1.0 x 10^–2mol dm^–3.
Calculate the partition coefficient for iodine between the organic solvent and water.

ii) The aqueous layer is separated and shaken with 50 cm3 of the pure organic solvent. What will be the concentration of iodine in the organic solvent at equilibrium in mol dm^–3?

Question 4

20g of butanedioic acid  were shaken with a mixture of 100 cm³ ether and 100 cm³ water at 298K. After titration with standard sodium hydroxide, it was noted that the ether layer needed 12.4mL of 0.2 mol dm^-3 solution for complete neutralisation. Calculate the partition co-efficient.

Question 5

100cm³ of an aqueous solution contains 4.0g of solute. 100cm³ of ether with a K_d of 3.8 is available to extract the solute.

Calculate the mass of solute extracted by the following amounts of solvent:

i) Single extraction using all 100cm³ of ether.

ii) The solvent is added as two consecutive 50cm³ volumes.

Question 6

Ammonia was extracted using silane and water. The concentration of ammonia was noted by means of titration, with the silane layer requiring 22.3mL of 0.01 mol dm^-3 HCl and and the water layer requiring 13.6mL of 0.2 mol dm^-3 HCl for complete neutralisation. Find K_d for ammonia between silane and water.

Question 7

Solute $S$ has a partition coefficient of $4.0$ between water and hexane.

(a) Calculate the concentration of $S$ in hexane if $[S_{water}$ is $0.044M$.

(b) If the volume of water is $87.0ml$ and the volume of hexane is $24.0\mathrm{mL}$, calculate the number of moles of S in each solvent.

Question 8

i) Calculate the partition coefficient of caffeine in water/ether from the following data: 12.4 g/100 mL for ether and 1.93 g/100 mL for water.

ii)  0.500 grams of caffeine is dissolved in 125 mL of water. 20mL of ether are used to extract caffeine from water. How much caffeine is in the ether? How much remains in the water? (use the partition coefficient as calculated in part i)

Question 9

The partition coefficient of aspirin between ether and water is 40.0. A solution contains 4.0 g of aspirin dissolved in 500Ml of water.

i) Calculate the mass of aspirin extracted when shaking with 50mL of ethoxyethane.

i) Calculate the mass of aspirin extracted when shaking with two successive portions of 25mL of ethoxyethane.

Harder Question

Question 10

A weak organic monobasic acid (HA) can be extracted using ether and water. 250 cm³ of a solution of HA in water, with a concentration of 0.049 mol dm^-3 was shaken with 250cm³ of water. the aqueous layer of has a pH of 3.57. Calculate K_d for this reaction

Hint: Knowledge of acids and basis is important. Find the concentration of acid in water using the K_a equation.