Module 2 Lab Report

An unknown substance "A" was allowed to partition between a mixture of 150 mL water and 80 mL benzene. After titration, you found that 0.75 moles of "A" was dissolved in the water while 0.60 moles dissolved in benzene. Calculate for the partition coefficient of substance "A". What can you infer about the nature of substance "A" based on the value of the partition coefficient?

If the concentration in a bulk solution adjacent to a fibrous medium is at a concentration cA = 1mM, and partition coefficient of K = 0.7, what is the concentration in the %3D leading edge of the fibrous medium? the answer has units of mM (canvas does not allow you to enter units or display the answer with units.) your answer mM

You add 1 mL of sample and collect 1 mL fractions from a column with a volume of 20 mL where the beads take up 60% of the column and the protein of interest has a partition coefficient of 0.4. What fraction do you want to keep?

Chemistry A 50ml aliquot of a 0.1 M solution of a neutral drug was extracted with 2 x 5 ml ethyl acetate. The drug concentration in the combined organic layers was found to be 0.36 M. Calculate the partition coefficient for this drug under these conditions.

Ethyl heptanoate (EH), a food aroma compound, was added to water and allowed to come to equilibrium with a known volume of air and results showed that its partition coefficient, [EHair]/[EHwater] is equal to 1.8 x 10-2. In the same experiment with oil in place of water, its partition coefficient, [EHair]/[EHoi] is found to be lower at 6.0 x 10-6. Account for the difference between the two values.

3

Partition coefficients (Kow = organic solvent concentration/aqueous concentration, usually reported as log Kow) are important for determining how efficiently organic compounds can be extracted from aqueous solutions. For example, consider the two substances below. Which will be more soluble in water? Hexamethylbenzene (log Kow = 6.41) O Diethyl ether (log Kow = 0.83)

4

2

The partition coefficient for caffeine between dichloromethane and water is 4.6.  Assume that a 100 mL tea solution (in water) contained 100 mg of caffeine.  What is the theoretical yield of caffeine in the methylene chloride if you extract with one 100 mL portion of methylene chloride?

If the partition coefficient of CBN from water into ethanol is 4, what fraction q of the CBN would remain in a 424 mL aqueous sample if it was extracted with 69 mL of ethanol twice?

Acetone has a partition coefficient of 13 while DCM has a partition coefficient of 4.6. Why is DCM used for the extraction of caffeine from Black teabags?

At 25 °C, the octanol-water equilibrium partition coefficient KOW of Compound X is 150,000 and its water-gas phase equilibrium partition coefficient KWA is 5000. Estimate the octanol-gas phase equilibrium partition coefficient KOA of Compound X.

Mercury is present in Lake Miramar at a total concentration of 20.4 ng/L. Lab tests suggest an average solids partition coefficient of 105L kg-1  What is the dissolved phase concentration if the particle concentration is 25 mg L-1?

A 78 mg sample of an organic compound (molar mass = 84.0 g/mol) is partitioned between 2.00 mL of water and 2.00 mL of methylene chloride. Separation and processing of the organic phase results in the isolation of 58 mg of the organic compound. Calculate the partition coefficient for the compound between methylene chloride and water (Kpmethylene chloride/water). Your answer should reflect the proper number of significant figures.

2) Assume you are decaffeinating your coffee by extracting the caffeine out with dichloromethane. Your particular brand of coffee contains 100 mg of caffeine in a 200 mL cup of water. The partition coefficient of caffeine in dichloromethane/water is 8.0 (it is more soluble in the dichloromethane).Answer the following questions about how much caffeine would still be in the 200 mL of water based on two different approaches. You should solve this algebraically. If you use an equation found on the internet, you will need to show how it was derived to receive credit.a) How much caffeine would remain in the water after extracting once with 200 mL of dichloromethane? Show your work.b) How much caffeine would remain in the water after extracting twice, each time with 100 mL of dichloromethane? Show your work.

The octanol - water aqueous buffer partition coefficients (P) for a drug used to treat glaucoma were obtained experimentally at various temperatures (T) and pH values. The results are presented in the following table: pH=7.0 0.72 0.84 pH=6.25 pH=7.25 T= 27 C 0.24 0.89 T= 30 C 0.31 1.06 T= 40 C 1.23 1.49 27.4 mg of this drug were dissolved in 100 mL of buffered water (pH=7.0; T=30) and then partitioned with octanol portions of 37.1 mL. Calculate how many mg of drug will remain in water after in the first extraction (Fill in ONLY numbers approximated to the 2nd decimal place) Answer: 19.01