Methodical instructions for the 1st year students
Medical faculty
LESSON 7 (6 HOURS)
THEMES:
1. Adsorption on the surface of liquids. Determining the influence of surfactants on the value of the surface tension
2. Adsorption on the surface of solid adsorbents
3. Ion-exchange adsorption
AIM:
To be able to determine the surface tension of liquids. To study the adsorption of colored substances on the surface of solid adsorbents. To be able to determine the content of pharmaceuticals and carry out desalting of water using ion exchange resins.
PROFESSIONAL ORIENTATION OF STUDENTS:
There are many interfaces in every living system, since the human body can be considered an aggregate of systems with extraordinarily developed surfaces. These are: the skin, walls of blood vessels, coverings of organs, membranes of cells, shells of intestinal flora microorganisms, etc. The majority of physiological processes, first of all respiration, excretion, take place on the surface of biomembranes. The action of both medicines and toxic substances on the human body also occurs with interface participation.
Adsorption in the body is important. Adsorption of different substances by blood cells and cytoplasm affects the metabolism. Such solid adsorbents as activated carbon and ion-exchange resins are used to remove foreign substances from the organism. Adsorption on solid adsorbents is widely used to purify vitamins, antibodies, antibiotics.
BASIC LEVEL:
1. Surface tension (secondary school course in physics).
2. Hardness of water (secondary school course in chemistry).
3. Dissociation and ion exchange reaction (secondary school course in chemistry).
STUDENTS’ SELF-PREPARATION PROGRAM.
Theme 1. Adsorption on the surface of liquids. Determining the influence of surfactants on the value of the surface tension
1. Surface tension and surface energy.
2. Surface-active agents (surfactants). Their structure and effect on surface tension. Traube’s rule.
3. Adsorption in a surface phase. Gibbs’s adsorption equation.
4. Methods of surface tension determination.
5. Surface phenomena of biological systems.
Theme 2. Adsorption on the surface of solid adsorbents
1. Basic aspects of adsorption. Definition: sorption, physical and chemical adsorption, absorption, adsorbents and adsorbates.
2. Dependence of adsorption on the nature of adsorbent and adsorbates.
3. Dependence of adsorption on the concentration and temperature.
4. Adsorption from solution at the solid surface.
5. Physical-chemical basis of adsorption therapy (hemosorbtion, plazmosorbtion, lymphosorption, enterosorption).
Theme 3. Ion-exchange adsorption
1. Adsorption of electrolytes: specific (selective) and ion exchange.
2. Fajans-Paneth rule.
3. Ion-exchange resins. Exchange capacity of ion exchanger. Determination of ion exchange capacity.
4. The use of ion exchange resins in medicine.
5. The concept of chromatography.
METHODOLOGY OF PRACTICAL CLASS. (900-1200)
Theme 1. Adsorption on the surface of liquids. Determining the influence of surfactants on the value of the surface tension
Work 1. To investigate the influence of different concentrations of isoamyl alcohol on the value of surface tension
Materials. isoamyl alcohol, stalagmometer, glass (beaker), measuring cylinder.
a) Preparation isoamyl alcohol solution with different concentrations:
Add 20 ml of distilled water to three glasses. Add 20 ml of isoamyl alcohol (this solution is diluted twice) to the first glass. Then take 20 ml of this solution and add to the second glass (this solution is diluted four times). Add 20 ml of four time diluted solution (this solution is diluted eight times) to the third glass.
b) Measure the surface tension of solutions of isoamyl alcohol by stalagmometer:
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Stalagmometer is the capillary glass tube which middle part is widened. In the experiment, the drops of the specific fluid are flowing slowly from the tube in a vertical direction. The drops hanging on the bottom of the tube start to fall when the volume of the drop reaches the maximum value, which is dependent on the characteristic of the solution. In this moment, the weight of the drops is in an equilibrium state with the surface tension. |
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Stalagmometer is washed twice with distilled water using a rubber bulb. Tighten distilled water above the top mark and count the number of drops of water volume between the marks of stalagmometer. Repeat several times. Find the average value (n0). Calculate the number of drops of each test solution of isoamyl alcohol (n).
WARNING! Start to measure the surface tension of the solution with the lowest concentration of isoamyl alcohol.
Surface tension is calculated by the formula:
Where:
nо – number of drops of water;
s0 – surface tension of water =73, J/m2;
n – number of drops of investigated solution;
s– surface tension of investigated solution.
Record the results in the table:
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Dilution of isoamil alcohol |
Number of drops |
Surface tension, J/m2·10-3 |
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water |
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72,75 |
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1:8 |
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1:4 |
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1:2 |
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Theme 2. Adsorption on the surface of solid adsorbents
Work 2. The study of adsorption of color substances from solutions.
Materials. Methyl blue solution, K2Cr2O7 solution, FeCl3 solution, Fe(OH)3 sol, konho red solution, fuchsine aqueous solution, activated charcoal, filtering paper, funnel.
Protocol: Take 6 test tubes and add 3 ml of the following solutions: methyl blue, K2Cr2O7, FeCl3, Fe(OH)3 sol, konho red, fuchsine. Then add to all test tubes the same quantity (≈
Record the result in the table:
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Name solution |
Methyl blue |
K2Cr2O7 |
FeCl3 |
Sol of Fe(OH)3 |
Konho red |
Fuchsine (aqueous) |
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color of the solution before adsorption |
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color of the solution after adsorption |
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Result |
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Theme 3. Ion-exchange adsorption
Work 3. Determining the total ion-exchange capacity of cation exchangers
Total ion-exchange capacity (EC) is an amount of mmol of ions that can adsorb
Materials: 0,1mol/l NaOH solution,
Protocol. Add
Work 4. Determination of drug substance (calcium gluconate) in solution by ion exchange adsorption.
If calcium gluconate solution passes through a column with cation-exchanger, gluconic acid is formed. Solution of this acid titrates with an alkaline solution.
WARNING! When working with column fluid level should not fall below the top-level of ion exchanger.
Materials: calcium gluconate solution, the column with cation-exchanger, 0,1mol/l NaOH solution, methyl orange indicator.
Protocol. 20 ml of calcium gluconate solution slowly passed through a column with cation-exchanger. Then 25 ml of distilled water slowly passed through the column in the same flask. Add 2-3 drops of methyl orange indicator and titrated 0,1 mol/l NaOH solution to all filtrate.
Calculate concentration of calcium gluconate by the formula:
Work 5. Desalting the tap water by using ion exchangers
Tap water contains many salts (e.g. calcium chloride). Qualitative reagent for Ca2+ is ammonium oxalate after mixing of which white precipitate calcium oxalate is formed. Qualitative reagent for the Cl– is silver nitrate after mixing of which white precipitate of silver chloride is formed.
If tap water passed through the column with cation-exchanger, the Ca2+ and other cations are exchanged for H+. The medium of water becomes acidic. If this water passes through the column with anion-exchanger, the Cl– and other anions exchange for
Materials: tap water, column with cation-exchanger, column with anion-exchanger, 0,5% (NH4)2C2O4 solution, 5% AgNO3 solution, methyl orange indicator.
Protocol: Qualitative test of Ca2+ and Cl–.
Add 5 drops of tap water and 2 drops of 0,5% (NH4)2C2O4 solution to the test tube. What is formed? Add 5 drops of tap water and 2 drops of 5% AgNO3 solution to the test tube. What is formed?
25 ml of tap water slowly passed through the column with cation-exchanger. Then 25 ml of distilled water slowly passed through a column in the same flask.
Check the presence of Ca2+ by the qualitative test and medium in the filtered water by methyl orange indicator.
25 ml of filtered water slowly passed through a column with anion-exchanger. Then 25 ml of distilled water slowly passed through a column in the same flask.
Check the presence of Cl– by qualitative test and medium in the filtered water by methyl orange indicator.
Work 6. Separation of ions Fe3+, Cu2+, Co2+ by chromatography on aluminum oxide
1 ml of mixture consisting of equal volumes of CuSO4, FeCl3 and CoCl2 solutions passes through the column with adsorbent (Al2O3). Watch how the liquid in the column is moving and colored chromatographic zones are formed. Paint the layers of adsorbent in matching colors.
SEMINAR DISCUSSION OF THEORETICAL ISSUES (1230-1400).
TEST EVALUATION AND SITUATIONAL TASKS.
Multiple choice tests
1. Which of the following does not belong to the surface phenomenon?
A. Adhesion.
B. Coatings.
C. Adsorption.
D. Sedimentation.
E. Occlusion.
2. Surface tension can be determined by the following method:
A. Potentiometry.
B. Chelatometry.
C. Stalagmometric method.
D. Chromatography.
E. Criometry.
3. What compound is surface inactive compound?
A. Alcohols.
B. Fatty acids.
C. Sodium
D. Amino acids.
E. Proteins.
4. What is adsorption?
A. Accumulation of one substance on the surface of the other.
B. Dissolution of one substance in the other.
C. Accumulation of one substance in the bulk of the other.
D. Chemical interaction of substances.
E. Mixing of substances.
5. What ion has the greatest adsorptive activity?
A. Sr+2
B. Са+2
C. Mg+2
D. Ba+2
E. Be+2
Examples of solving tasks
Task 1. Calculate the value of adsorption at
Answer:
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m(C8H17COOH)= σ(water)= 74,2·10-3 J/m2 σ(C8H17COOH) = 57·10-3 J/m2 |
Gibbs equation for the liquid-gas adsorption:
Determine the concentration of acid in solution:
Calculate the value of adsorption:
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Г-? |
Task 2. Find the area occupied by one molecule in the saturated adsorption layer on the surface of the aniline of its aqueous solution, if the maximum adsorption is equal to 6,0·10-6 mol/sm2.
Answer:
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Гmax=6,0·10-6 mol/sm2 |
The area occupied by one molecule of a substance:
Calculate:
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S0-? |
Task 3. Calculate the length of butyric acid molecule if the area occupied by one molecule in the surface layer is S0 = 3,2·10–
Answer:
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S0 = 3,2·10– ρ= 978 kg/m3; M(C3H7COOH)=0,088 kg/mol |
The length of molecule is calculated by the equation:
From the equation
Calculate the length of butyric acid:
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l = ? |
Task 4. Calculate the mass of Na+ ions in NaCl solution. For the titration of filtrate obtained after passing through cation-exchangers in H+-form 7,25 ml HCl solution with an equivalent molar concentration C(HCl) = 0,1 mol/l was used.
Answer:
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V(HCl)=7,25 ml C(HCl) = 0,1 mol/l. |
To calculate the mass of ions we used the formula:
Equivalent mass of Na+ = molar mass Na = 23 Calculate the mass of ions:
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m(Na+) – ? |
Tasks
Task 5. Calculate the surface tension of aniline, if the following results were obtained by stalagmometer’s method: number of drops of aniline n=42, number of drops of water n0=18. Surface tension of water sо=72,75´10–3 J/m2.
Task 6. Calcium gluconate solution passes through Н-cation-exchanger. For the titration of 40 ml of filtrate 8 ml of NaOH solution with an equivalent molar concentration of 0,1 mol/l was used. Calculate concentration of calcium gluconate?
Task 7. Calculate the value of adsorption of hexanoic acid solution (С5H11COOH) at
Task 8. The concentration of two aqueous solutions of caproic acid is 0,005 and 0,01 mol/l at 273 K. The surface tension of these solutions is 65,8·10-3 J/m2 and 60,05 10-3 J/m2 accordingly.Calculate the value of adsorption.
Task 9. Calculate the length of one surfactant molecule if Гmax=8,5·10-6 mol/m2, M(x)=0,074 kg/mol, ρ=800 kg/m3.
Task 10. Calculate the mass of Cl– ions if it is known that for titration of the filtrate that was obtained by its passing through an anion-exchangers in the OH–-form 5 ml of H2SO4 solution was used with an equivalent molar concentration C(H2SO4) = 0,1 mol/l
Student should know:
· Surface tension.
· Surface-active agents (surfactants). Traube’s rule.
· Adsorption from solutions on solid adsorbent.
· Molecular adsorption of non-electrolyte.
· Adsorption of electrolytes from solutions, the Fajans-Paneth rule.
· Biological importance and practical application of adsorption.
· The concept of chromatography.
Student should be able to:
· Measure surface tension of liquids.
· Determine the concentration of drug substance by ion exchange adsorption.
· Desalt the tap water by using ion exchangers.
· Calculate surface tension, value of adsorption, length of surfactant molecule.
Correct answers of test evaluations and situational tasks:
Multiple choice tests
1. D; .2. C;
Tasks
5. 31,18·10-3 J/m2
6. 0,43%
7.
8. 3,82·10-6 mol/m2
9.
10.
References:
1. http://intranet.tdmu.edu.ua/ Student’s facilities /Lecture presentations /Department of General Chemistry/ English / medical /1 course/ medical chemistry/ 08. Physical-chemical essence of surface phenomenon
2. http://intranet.tdmu.edu.ua/ Student’s facilities /Practical classes materials /Department of General Chemistry/ medical chemistry/ medical/ 1 course/ English/ 07. Surface tension. Adsorption.
3. Atkins, Peter W.; de Paula, Julio. Physical Chemistry (9th ed.).
4. Physical Chemistry of Surfaces, by A. Adamson & A. Gast, 6th Ed. Wiley, 1997, ISBN-0-471-14873-3.
5. Surface Chemistry and Catalysis, by Gabor A. Somorjai. Wiley,
6. Monk, Paul M. S. Physical chemistry: understanding our chemical world / Paul Monk. Wiley,
7. Chemistry” 3th ed. J. Mc Murry and R. Fay; – Prentice Hall,
Methodical instructions have been worked out by:
Associate Prof. Kyryliv M. V.
Methodical instructions were discussed and adopted at the Department sitting
27 August 2013. Minute № 1
