Thus, 0.999935·10–4 kg of iodine is extracted. Upon using the same volume of carbon disulphide, in the case of single extraction 96.7% is separated, while in the case of 5-fold multiple extraction, basically, iodine is extracted completely.

Answer: a) 3.3·10–4 kg of iodine remain unextracted. b) 6.5·10–9 kg of iodine remain unextracted.

Problems

Problem № 1. The equilibrium concentrations of iodine in water and carbon tetrachloride at 25°С are given in the table below.

Concentration of iodine, g/L ×·106

Find the distribution coefficient of iodine between CCl4 and water. Determine the amount of carbon tetrachloride needed to extract 95% of iodine from 500 mL of its aqueous solution using the single extraction method.

Problem № 2. How much phenol is extracted from 1 L of a 0.2 M aqueous solution by 300 mL of pentanol? To which degree of completeness does the extraction proceed if it is performed with 3 portions of pentanol with a volume of 100 mL each? Use the value of the distribution coefficient found in the handbook of physicochemical quantities.

Problem № 3. The equilibrium concentrations of succinic acid in water and ether at 15°С are given in the table.

Concentration of succinic acid, mol/L

Find the distribution coefficient of succinic acid between ether and water. Calculate the amount of water required for extraction of 90% of

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succinic acid from 400 mL of its ethereal solution using the single extraction method?

Problem № 4. 5 L of an aqueous solution of iodine with a concentration of 0.2 g/L are extracted fractionally at 18°С by two separate 200-mL portions of carbon tetrachloride. How much iodine does remain in an aqueous solution after extractions? What will be the amount of remnants in the case when carbon disulphide is used instead of ССl4? Use the corresponding values of distribution coefficients from the handbook of physicochemical quantities.

Problem № 5. What is the number of extractions needed to extract 99% of iodine by 100-mL portions of pentanol from 2 L of an aqueous solution at 25°С? Use the distribution coefficient value from the handbook of physicochemical quantities.

Problem № 6. At temperature of 288 K, an aqueous solution containing 12.1 g/L of succinic acid is in equilibrium with its ethereal solution, the concentration of which is 2.2 g/L. What is the concentration of an ethereal solution of succinic acid that is in equlibrium with its aqueous solution containing 4.84 g/L of the acid? Succinic acid has normal molecular weight both in water and ether.

Problem № 7. The following concentrations (kg/m3) were found upon partition of acetic acid between carbon tetrachloride and water:

in ССl4………………...2.92 3.63 7.25 10.7 14.1; in Н2О…………….…..48.7 54.2 76.4 93.0 107.0.

Acetic acid in an aqueous solution has normal molecular weight. Determine the molecular weight of acetic acid in CCl4 and the distribution coefficient between the two solvents.

Problem № 8. The following concentrations (kmol/m3) were obtained upon distribution of phenol between water and benzene:

Calculate the distribution coefficient, K, and the exponent, n, in the formula describing the partition law.

Problem № 9. Phenol has normal molecular weight both in water and amyl alcohol. At a temperature of 298 K, a solution containing 10.53 g/L of phenol in amyl alcohol is in equilibrium with an aqueous solution containing 0.658 g/L of phenol. Determine the weight of phenol that can be

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obtained from 0.5 L of its aqueous solution with a concentration of 37.6 g/L by double extraction with amyl alcohol. 0.1 L of amyl alcohol was taken in each extraction step.

Problem № 10. The distribution coefficient of iodine between water and carbon tetrachloride at 298 K equals 0.0117. Iodine has the same molecular weight in both solvents. What is the volume of carbon tetrachloride needed to extract 99.9, 99.0, and 90.0% of all iodine contained in 0.5 L of water using the single extraction method?

Problem № 11. What amount of iodine remains in 1 L of an aqueous solution, which has been preliminarily saturated at 291 K, after its stirring with 0.1 L of carbon disulphide? The solubility of iodine in water at 291 K is 1 g per 3.616 L. Take the distribution coefficient of iodine between water and carbon disulphide as equal to 0.001695. Iodine has the same molecular weight in both solvents.

3.4.REFERENCES

1.Ippolitov, E.G. Physical chemistry: textbook for chemistry students of higher education institutions / E.G. Ippolitov, A.V. Artemov, V.V. Batrakov. − М.: Akademiya, 2005. – 448 p. [In Russian]

2.Stromberg, A.G. Physical chemistry: textbook for chemistry students of higher education institutions / A.G. Stromberg, D.P. Semchenko. – 5th ed., corrected. − М.: Vysshaya shkola, 2003. – 527 p. [In Russian]

3.Krasnov, K.S. Physical chemistry: textbook for higher education institutions: in 2 vol. / K.S. Krasnov. – 3rd ed., corrected. − М.: Vysshaya shkola, 2001. [In Russian]

4.Zimon, A.D. Physical chemistry: textbook for technology students of higher education institutions with non-chemical profile / A.D. Zimon, N.F. Leshchenko. – М.: Khimiya, 2000. – 318 p. [In Russian]

5.Atkins, P. Physical chemistry / P. Atkins, J. de Paula. – 9th ed. – New York: W.H. Freeman and company, 2010. – 1060 p.

6.Kudryashov, I.V. Collection of exercises and problems in physical chemistry / I.V. Kudryashov, G.S. Karetnikov. − 6th ed., corrected and revised. − М.: Vysshaya shkola, 1991. – 527 p. [In Russian]

7.Mishchenko, K.P. Practical exercises in physical chemistry: study guidance for chemical-engineering higher education institutions / K.P. Mishchenko, A.A. Ravdel, A.M. Ponomaryova. – 4th ed., corrected and revised. – Leningrad: Khimiya, 1982. – 399 p. [In Russian]

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8.Baron, N.М. Short handbook of physicochemical values: reference book / N.М. Baron [et al.]; ed. by A.A. Ravdel, A.M. Ponomaryova. – 10th ed., corrected and revised. – SPb.: Ivan Federov, 2002. – 238 p. [In Russian]

9.Ponomaryova, A.M. Phase equlibria and theory of solutions: study guidance / A.M. Ponomaryova. – Saint Petersburg: Saint Petersburg state technical university, 1992. – 159 p. [In Russian]

10.Zenin, G.S. Physical chemistry. I Part. Chemical thermodynamics: text of the lectures / G.S. Zenin, T.A. Privalova, N.V. Penkina. – SPb.: North-west state extra-mural technical university, 2001. – 77 p. [In Russian]

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