.. BeSafe Airtel LTE 12:15 PM 86% critical micelle concentration Experiment 2 Critical micelle concentration of surfactant 1. Objective 1. To determine critical micelle concentratice (CMC) of 2 ne surfactant, sodium dodecyl sulphate 1.2 To learn the conductometric method for me, CMC nie surfactants 2. Introduction Surfactant is an amphiphilie substance that comes of both polar and non-polar parts. When a small amount of surfactant is disainit mainly exists as monomers dispersed in water Based on its structural properties, the surfactant will be adsorbed on the surface of the solution with a preferred mentatieAs the concentration increases, it will agregate and for me to make bestable in solution, the surfactant changes in two ways to leave the hydrophilic groups in the water and to let the hydrophobic groups facing the deather another is to collect the hydrophobic groups of the surfactant in order to reduce the interfacialaren with water. The former reduces the surface tension and leads to the adoption of the surfactant on the interface and the formation of inted mone-selecular membrane The latter leads to the formation of micelle Since the bydrophilic groups of the micelle constitute iscutere continenting with the water molecules the surfactantis stable in solution. As the surfactant concentration further the spherical micelle may change to clavicom micelle, or even to lamellarmcelle The minimum concentration of surfactant which micelle formation bei referred to as the critical micelle concentration, CMC which is a very important property for surfactant. Above the CMC, the physical and chemical properties (such as surface con conductance, we pressure, turbidity optical property) change abruptly with concentration owing the change in solution structure This phenomenon is an important characteristic of surfactants and also the base of CMC measurments. In this experiment, the conductivities formalarconductivities of sodium dodecyl sulphate of different concerned using conductometer. The CMC is obtained from the discoile bees in the teabetween conductivity and concentration 3. Apparatus and Reagent Conductometer, thermostatic water bottletrie flank comicul flaske sodium dodecyl sulphate. 4. Procedure 4.1. Prepare a series of sodium dodecyl sulphate solutions with different concentrations with pure water 42. Tum on the thermostatic water bath und adjust the temperame of the thermostat to 25 43. Measure the conductivities of the above solutie Wash the strade with distilled water. Rinse the comical flank with the test is over three times before each measurement. Let the flask and the solution warm for 10 min efore mesurement 1/2 !!! 0-
.. BeSafe Airtel LTE 12:15 PM O 86% critical micelle concentration 4.4. Tabulate the data of the conductivities of the solutions 4.10 Wash the tubes and electrodes with distilled water after experiment 5. Data Analysis 5.1. Plot the conductivities against concentrations, and find out the CMC from the furning point in the plot 5.2. Reference data at 25 C, CMC of sodium dodecyl sulphate is about 8.0 – 10+ mol/L 6. Notes Al Electrodes must be wiped to dry after washing to ensure the precision of the concentrations of solutions 62. The conductometer must be adjusted before measurement 7. Exercises 7.1. What are the factors that influence the measurement of CMC of one surfactant? 7.2. To identify whether the measured CMC is correct, what kind of experimental technique can be used? 2/2 = III O-
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