Determination of Critical Micelle Concentration

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Determination of the Critical Micelle Concentration|
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Introduction:
Purpose: The purpose of this experiment is to use the Conductometric method to determine the critical micelle concentration of SDS. Materials and Equipment:
* SDS- Sigma Aldrich, Lot: 38H0080, S/N: L-439,
* NaCl- Food grade Great Value
* SDS 20% solution- Fisher Biotech, S/N: BP1311-200, Lot: 468059 * Wave generator- Pasco Scientific, S/N PI-9587C
* Ammeter- Keithley Auto-ranging Multimeter, Model: 175A, S/N: 0690266 * Oscilloscope- Protek 6506 S/N: 650602332
* Heating mantle/mixer- Cimatec 2 Thermolyne, Model: SP46925, S/N: 1069020639876 * Analytical Balance- Denver Instrument Co., A-250, S/N: 100007, P/N: 201169 Procedure:
Part 1: Pure Water
* All materials needed were collected. (SDS 20% solution was only SDS attained at this time) * Two carbon rods were dipped in paraffin and completely covered except for the bottom tips to create electrodes. * These were put in series with a waveform generator and an ammeter. * This was incorrectly done the first time.

* A solution of the 20% SDS solution was made and tested in the incorrect set up. * It was concluded that the wave generator needed to be adjusted and new SDS needed to be found. * Proper SDS was found and the set up was corrected.

* 50 mL of a 0.04 M aqueous solution was made by mixing 50 mL of purified water and 0.58 g of SDS * 50 mL of purified water was placed in a beaker with a stir bar. * The electrodes were rinsed with water and placed into the beaker well below the surface of the water. * The stirrer was turned on to the lowest speed.

* The ammeter was set to the 2-mA range and the waveform generator was set at 1 kHz and the wave generator’s square wave properties were checked with the oscilloscope. * A 0.5 mL calibrated pipet was used to deliver one aliquot of the SDS solution to the beaker every 15 seconds until 40 aliquots had been added. The current was recorded after each 15 seconds. Part 2: Added Electrolyte

* The same series set up was used.
* A 100 mL, 0.01 M solution of NaCl was made by mixing 0.0578 g of NaCl and 100 mL of water. * This solution was used to make 25 mL of a 0.04 M solution of SDS. (25 mL mixed with 0.578 g of SDS) * 50 mL of the NaCl solution was put into the beaker with the electrodes. * A 0.3 mL calibrated pipet was used to deliver one aliquot of the SDS solution to the beaker every 15 seconds until 30 aliquots had been added. The current was recorded after each 15 seconds. * The same procedure (Part 2) was repeated using a 0.02 M NaCl solution and 0.2 mL aliquots. Data:

Aliquots Added| Part 1: Pure Water Current (mA)| Part 2: Added Electrolyte 0.01M Current (mA)| Added Electrolyte 0.02M Current (mA)| 1| 0.101| 0.5793| 0.5828|
2| 0.176| 0.6322| 0.6385|
3| 0.246| 0.6787| 0.688|
4| 0.314| 0.733| 0.7301|
5| 0.372| 0.7994| 0.7801|
6| 0.423| 0.8464| 0.8234|
7| 0.478| 0.8908| 0.8636|
8| 0.527| 0.9379| 0.9067|
9| 0.569| 0.9763| 0.9362|
10| 0.596| 1.0062| 0.9666|
11| 0.634| 1.0406| 0.9902|
12| 0.64| 1.0682| 1.0284|
13| 0.669| 1.0966| 1.0568|
14| 0.7| 1.1264| 1.082|
15| 0.728| 1.1507| 1.1172|
16| 0.758| 1.18| 1.1368|
17| 0.783| 1.206| 1.1579|
18| 0.803| 1.2328| 1.1753|
19| 0.821| 1.2509| 1.2005|
20| 0.843| 1.2704| 1.2216|
21| 0.866| 1.289| 1.2425|
22| 0.888| 1.3094| 1.2581|
23| 0.907| 1.329| 1.2789|
24| 0.923| 1.343| 1.296|
25| 0.94| 1.3576| 1.3138|
26| 0.953| 1.3731| 1.3348|
27| 0.963| 1.3854| 1.3422|
28| 0.975| 1.3934| 1.3552|
29| 0.983| 1.4138| 1.3693|
30| 0.991| 1.4236| 1.3818|
31| 1| -| -|
32| 1.006| -| -|
33| 1.015| -| -|
34| 1.021| -| -|
35| 1.031| -| -|
36| 1.037| -| -|
37| 1.043| -| -|
38| 1.05| -|...
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