FLORES-CMC-ILAR-2017.docx

University of San Carlos Department of Chemical Engineering Talamban, Cebu City, Philippines 6000

Individual Laboratory Report Laboratory Course:

CHE 412L – Physical Chemistry Laboratory II

Experiment Title:

Conductimetric Determination Determination of the Critical Micelle Concentration of Sodium Dodecyl sulfate (CMC)

Student’s Name and Signature:

Flores, Dharyl C.

Scheduled Date:

August 16, 2017

Date Performed:

August 18, 2017

Date Submitted:

October 25, 2017

Submission Number:

1

Instructor:

Engr. May V. Tampus

Term and Academic Year:

1st Semester, A.Y. 2017-2018

Data Processing and Results

Grade

Introduction (x0.20) Methodology (x 0.20) Presentation of Results (x 0.20) Discussion of Results and Conclusions (x 0.20) Writing Style (x 0.10) Appearance and Formatting (x 0.10) Grade

Assessed and Graded By:

Engr. May V. Tampus (Signature over printed name)

Date and Time

October 25, 2017

University of San Carlos – Department of Chemical Engineering CHE 323L FORM-2-Individual Laboratory Report Rating

University of San Carlos Department of Chemical Engineering Talamban, Cebu City, Philippines 6000

CHE 412L

P hysica hysi call Che C hem mi stry L abor ator tor y 2

Conductimetric Conductim etric Determination of the Critical Micelle Concentrat Concentration ion of Sodium Dodecyl sulfate (CMC)

A laboratory report submitted to

Engr. May V. Tampus CHE 412L Instructor

by

Flores, Dharyl C.

October 25, 2017

1


1. Introduction

Surfactant is an abbreviation for surface-active agent, which includes molecules that are active at surfaces. These molecules have a tendency to reside rather at the surface than in bulk solutions due to their amphiphilic nature. Amphiphilic molecules consist of at least two parts: one of which being hydrophobic and the other hydrophilic. A typical surfactant molecule consists of a long hydrocarbon “tail” that dissolves in hydrocarbon and other nonpolar solvents (water-insoluble; hydrophobic), and a “headgroup “that dissolves in polar solvents (typically water; hydrophilic) as shown in Figure 1. Surfactants have two main features making them essential; one of them is the tendency to adsorb at interfaces and lower the surface tension and the other is the association in solution.

Figure 1. Schematic Representation of a Surfactant (Bucak & Rende, 2014) Surfactants have the general formula RX, in which R is a hydrocarbon chain and X is a polar group. The hydrocarbon chains in the molecule are ordinarily C 8 or greater, may be saturated or unsaturated, may be linear or branched, and may contain an aromatic ring. However, the polar group in the amphipathic molecule may be nonionic or ionic. Sodium dodecyl sulfate or sodium lauryl sulfate

(), a common anionic surfactant, was

used in the experiment for the determination of its critical micelle concentration (CMC) in a different solution — pure water and 0.02 M aqueous NaCl solution. The amphiphilic ion is

− while + is the counter ion. 2


The increase in the concentration of a particular surfactant in an aqueous solvent reveals a sudden change in various aqueous surfactant solution physico-chemical properties such as surface tension, equivalent conductivity, solubilization, osmotic pressure, turbidity, selfdiffusion, magnetic resonance, UV-visible/fluorescence spectra of solutes, and reaction rates above a sharp surfactant concentration (Khan, 2007). Such changes in various physical properties of an aqueous solution of the surfactant are attributed to the formation of aggregates of surfactant molecules above a critical surfactant concentration, which is termed as critical micelle concentration (CMC), because these surfactant molecular aggregates are called micelles. Micelles are colloid-sized clusters of molecules; whose hydrophobic tails tend to congregate through hydrophobic interactions while their hydrophilic head groups provide protection. Micelle formation among surfactant molecules takes place when their hydrophobic ends collect themselves away from the water molecules while the hydrophilic ends surround them and are the ones oriented toward the water molecules. The centers of these micelles are somewhat hollow so that they can still accommodate a few more molecules and thus, water with surfactant micelles can now easily dissolve the otherwise insoluble hydrocarbons (Atkins and de Paula, 2010).

Figure 2. Schematic diagram of a Spherical Micelle (Atkins and de Paula, 2010)

Micelles form only above the critical micelle concentration (CMC) and above the Kraft temperature. The CMC is detected by noting a pronounced change in physical properties of 3


the solution, particularly the molar conductivity. There is no abrupt change in properties at the CMC; rather, there is a transition region corresponding to a range of concentrations around the CMC where physical properties vary smoothly but nonlinearly with the concentration (Atkins and de Paula, 2010).

Figure 3. The typical variation of some physical properties of an aqueous solution of sodium dodecyl sulfate (SDS) close to the CMC (Atkins and de Paula, 2010)

2. Objectives of the Experiment

1. To measure the conductivity of an aqueous sodium dodecyl solution at different concentrations 2. To determine the critical micelle concentration of an aqueous SDS solution 3. To determine the effect of the presence of an electrolyte on the critical micelle concentration of an aqueous SDS solution

4


3. Methodology

3.1. Methodological F ramework Preparation of sodium dodecyl sulfate (SDS) and aqueous sodium chloride solutions.

Calibration of conductivity meter with 0.01 N KCl solution as standard solution.

Determination of Critical Micelle Concentration (CMC) of SDS solution.

Determination of Critical Micelle Concentration (CMC) of SDS solution.

3.2. Materials Materials used were Ssodium dodecyl sulfate (NaOSO3C12H25) solution, potassium chloride (KCl) and sodium chloride (NaCl) aqueous solutions.

5


3.3. E quipment The equipment used for this experiments were the Orion Star A215 pH/Conductivity Meter which is used to measure the conductivity of the samples. Also, analytical balance, weighing boats, pipette and pipettor, stirring rod, magnetic stirrer, beakers and wash bottle were used.

3.4. Procedures Preparation of Solutions For the preparation of 0.5M sodium dodecyl sulfate (NaOSO3C12H25), 1.5178 g of sodium dodecyl sulphate was weighed, dissolved, and diluted to 100-mL in a 250-mL beaker. Another sample was prepared using the same procedure. For the preparation of 0.2 M aqueous NaCl solution, 1.6770 g of solid NaCl was weighed, dissolved and diluted to 100-mL in a 250-mL beaker. For the preparation of standard (0.01 N) KCl solution, 10-mL of standard solution was pipetted and diluted with distilled water to 100-mL.

Calibration of C onductivity Meter with Standard KCl Solution Initially, the conductivity meter was turned on and measurement mode was set to conductivity. The conductivity cell and the electrodes were then connected to the meter also. In the measurement mode, f1 (cal) was pressed. In order to highlight the conductivity-channel, the “set-up” or “log/print” was pressed then the f2 (select). After, the electrodes and conductivity cell were rinsed with distilled water using the wash bottle and dr y it with a lint-free tissue before immersing it into the prepared standard (0.1 N KCl). Next, f3 (start) was pressed to begin the calibration. Until the conductivity value on the meter remained constant, f2 (accept) was pressed to display the cell constant. 6


Conductivity Measurement for CMC of SD S in Pure water In a clean 200-mL beaker, 70-mL of distilled water was measured and pipetted. The beaker was placed in top of a magnetic stirrer and inside it a small stirring bar. The conductivity cell and other electrodes were then set up and the settings were set. The value of the measured conductivity was than measured. Using a pipet, 0.3-mL of the prepared solution of SDS was added. The conductivity was then recorded again. 0.3-mL aliquots of the SDS solution were continuously added every minute and the readings of conductivity were recorded every addition. After 15 aliquots of 0.3-mL SDS solution were added, instead of 0.3-mL, 0.5-mL of SDS solutions were now added and the conductivity were recorded every addition.

Conductivity Measurement for CMC of SD S in NaCl solution The same procedure was employed as the conductivity measurement for CMC of SDS in Pure water to SDS in 0.02M NaCl solution, except that 45 more additions of 0.2-mL aliquots of SDS solution were added.

4. Results and Discussions

Objective 1: To measure the conductivity of an aqueous sodium dodecyl solution at different concentrations The conductivity meter (Polyscience Model 4010) was used to measure the conductivity of an aqueous sodium dodecyl sulfate solution at different concentrations. Before determining the conductivity of the surfactant solution, there is a need for calibration of the conductivity meter apparatus by immersing the conductivity cell into 0.01 N KCl solution. The data gathered in the calibration is shown in Table 1 below.

7


Table 1. Calibration of Conductivity Meter with 0.01N KCl standard solution Conductivity of 0.01N KCl Solution ( Cell Constant (

/)

− )

0.431

℃) Temperature Reading ( ℃)

30

Temperature Displayed (

RPM of Magnetic Stirrer

1413

30

  

400

Concentration of KCl Solution (eq KCl/L sol’n)

0.01

Concentration of NaCl Solution (mol NaCl/L sol’n)

0.02

Concentration of SDS Solution (mol SDS/L sol’n)

0.05

In the measurement of the conductivity of aqueous sodium dodecyl sulfate solution at different concentrations, 70-mL of distilled water is put inside a 100ml beaker. Then this was placed on top of a magnetic stirrer which operates in the settings shown in Table 1. The conductivity of water is then read and tabulated. Using a 1-mL pipette, 0.3-mL aliquots of 0.05 M SDS solution was added into the beaker every 1-minute interval for the first 15

8


minutes. After the 15 additions 0.5-mL are added into the solution for every 1-minute interval. This is done while reading and recording the conductivity of the solution with each aliquot addition.

600.00

500.00 ) m c 400.00 / S µ ( y t i v i t c u d n o C

300.00

200.00

100.00

0.00 0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

Concentration (mol/L)

Figure 4. Conductivity Measurements of Aqueous Sodium Dodecyl Solutions at Different Concentrations From Figure 4 above, it can be observed that the conductivity of the solution increases as the concentration of SDS in the solution increases. Though the magnitude of the increase of conductivity with concentration varies at a point. It can be seen that there is a greater increase in the conductivity of the solution with every increase in concentration before the intersection of the two trend lines, than after the intersection. This is evidenced by the greater value of the slope of the first trend line

∙ than in the second trend line 34355 ∙ . 61891 ∙ ∙

This is because, the conductivity of a solution is dependent on the number of charge carriers (ions) present in it. Before CMC point, the addition of the surfactant SDS into the solution will tend to increase the number of cations and anions in the solution since SDS, when added to the solution, will dissociate into

+ and   − ()   () 9

ions and therefore, it is expected that


the solution’s conductivity increases as more SDS is added. After the CMC point, upon addition of SDS into the solution, the SDS will not anymore ionize into

+ and   − ions but ()   ()

instead cause micelle nucleation which would increase the micelle concentration upon further SDS addition but would leave the monomer (ions) concentration unchanged. And since micelles are bulkier than that of

+ and   − ()   ()

ions they move slower and thus are less

effective charge carrier causing smaller increase in conductivity of the solution with increase in SDS concentration than what was observed before reaching the CMC. Objective 2: To determine the critical micelle concentration of an aqueous SDS solution One of the fundamental properties of surface-active agents is the self-assembly of surfactant molecules in the bulk solutions to form aggregates with different geometries like disks, spheres, cylinders, etc. The simplest aggregates are generally spherical in shape and are called micelles. However, this phenomenon occurs only when the surfactant concentration exceeds a threshold known as the critical micelle concentration (CMC). In a micelle, the hydrophobic part of the surfactant molecule is directed toward the interior of the cluster and the polar headgroup toward the aqueous solution as shown in Figure 1a. When a surfactant adsorbs from aqueous solution at a hydrophobic surface, it orients its hydrophob ic group toward the surface and exposes its polar group to water as shown in Figure 1b. The driving force for self-assembly is said to be the hydrophobic effect. As micelles form as shown in Figure 1c, sharp changes occur in many physical properties such as the surface tension, viscosity, conductivity, and sometimes turbidity of the solution.

10


Figure 5. Surfactant Behavior in Aqueous Solutions (Bucak & Rende, 2014) The critical micelle concentration (CMC) is usually determined experimentally by plotting some property as a function of concentration and extrapolating the results at low and high concentrations to an intersection point (Lindman & Wennerstrom, 1980). That is, at the said point shows a significant change of a physico-chemical parameter, where for this experiment is

260000

210000 ) l o160000 m -

m c / 110000 L S µ ( C / 60000 k

10000 0 -40000

0.01

0.02

0.03

0.04

0.05

0.06

0.07

C1/2 (mol/L)1/2

11

0.08

0.09

0.1

0.11

0.12


conductivity. The determination of the critical micelle concentration (CMC) was done through graphical means which is discussed in detail in the below.

1. Conductivity of solution per molarity of solution (  /C) vs. the square root of the SDS concentration (C 1/2 )

260000

210000 ) l o160000 m -

m c / 110000 L S µ ( C / 60000 k

10000 0

0.01

0.02

0.03

0.04

0.05

-40000

0.06

0.07

0.08

0.09

0.1

0.11

0.12

C1/2 (mol/L)1/2

Figure 6. CMC Determination from the Plot of /C vs C1/2 of SDS in Pure Water at T= 30.7 , 400 RPM

℃

In this plot, two tangent lines were drawn and since the point of intersection is away from the graph and the corresponding c 1/2 value cannot be directly determined, the angle bisector of the angle formed by the two lines was drawn and its point of intersection with the graph was determined to find the c 1/2 value. The critical micelle concentration was determined by squaring this value. From this plot, the square root of the critical micelle concentration of the aqueous SDS solution obtained is this plot is

3.40 ×10−   . Squaring this value, the critical micelle concentration from

1.1560×10−   . The ratio between conductivity and concentration, k/C, is known as 12


molar conductivity,

λ . As observed in Figure 6, there is a drastic change in the molar conductivity

of the solution from the starting square root of concentration until it reaches the critical micelle concentration. Small amounts of SDS was added into the distilled water. At the beginning of the experiment, a dilute solution of SDS was formed where its concentration is below its critica l micelle concentration. Below the critical micelle concentration, SDS behaves as a normal electrolyte wherein when dissolved in water, it ionizes to produce

+ and   − . The addition ()   ()

of a surfactant to an aqueous solution causes an increase in the number of charge carriers (

+ and   − for SDS) and consequently, an increase in the conductivity. At these ()   ()

low concentrations, below the CMC, only monomers exist in the solution. As the amount of the SDS solution was added to the water, the number of monomers increased. The SDS solution was continuously added then it reached to a point that the amount of this surfactant added was equal to the critical micelle concentration. At this point, micellization occurred. In addition, it is at this point that micelles start forming, being in equilibrium with the monomers. The increase in the concentration of SDS in water above CMC, caused nucleation for the micelle to form. Thus, there is an increase of in the concentration of micelles in the solution. However, the concentration of monomers remained unchanged in the solution. Since a micelle is much larger than a monomer, it diffuses more slowly through solution and so is a less efficient charge carrier (Bucak & Rende, 2014). According to Kohlrausch’s law that at low concentrations the molar conductivities of strong electrolytes (substances that are fully dissociated into ions in solution) vary linearly with the square root of the concentration:

Λ = Λ°   /

13


where

Λ = ,  is the conductivity, c is the concentration of the added electrolyte and Λ is the

molar conductivity of solution. This variation is called Kohlrausch’s law. The constant

° is the

limiting molar conductivity, the molar conductivity in the limit of zero concentration (when the ions are effectively infinitely far apart and do not interact with one another). The constant K is found to depend more on the stoichiometry of the electrolyte than on its specific identity. The

/

dependence arises from interactions between ions: when charge is conducted ionically, ions of one charge are moving past the ions of interest and retard its progress (Atkins and de Paula, 2010). Objective 3: To determine the effect of the presence of an electrolyte on the critical micelle concentration of an aqueous SDS solution The critical micelle concentration (CMC) is at the point at which surfactant molecules aggregate together in the liquid to form groups known as micelles. The CMC of a surfactant indicates the point at which surface active properties are at the optimum and performance is maximized. However, the presence of other component, in particular, electrolytes such as inorganic builders and alkali consequently decreases the CMC of a surfactant. This reduction affects the adsorption, wetting and emulsifying properties of surfactants (Savale, 2016). In the experiment, the effect of sodium chloride aqueous solution on micellar systems of an anionic surfactant such as sodium dodecyl sulfate was studied. It has been observed that the critical micelle concentration (CMC) decreases with the presence of an electrolyte than pure water alone. The effect of additives on CMC of an aqueous solution of a surfactant depends on the nature of interaction between additive and micellized surfactant molecules. Molecular interaction between interacting molecules may involve some or all of the following interactions: dipole –dipole, ion –dipole, ion –ion, van der Waals/dispersion forces, and hydrogen bonding. Energetically favorable interactions between additive and micellized surfactant molecules will increase the stability of micelle, which will, in turn, cause the decrease in CMC. 14


175000

140000

) l o m -

105000

m c / L S 70000 µ ( C / 

35000

0 0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

C1/2 (mol/L)1/2



Fi g ure 7. C MC Determination from the Plot of /C vs / of S DS in 0.02 M Aqueous NaCl S olution at 30.3 , 400 rpm

℃



As shown above, the experimentally determined critical micelle concentration of sodium dodecyl sulfate at 30.3

℃ and 400 rpm is 8.4100 ×10− /. The technique employed was

done similarly to the previous method described in Objective 2. The trend is almost the same with that of the determination of CMC in pure water except that in this curve, it is almost approaching linearity at a constant molar conductivity value. Moreover, a lesser addition of SDS solution to the electrolyte solution of NaCl was needed for the change in conductivity to approach a constant value.

Table 2. C ritical Micelle Concentration of S DS in P ure Water and in 0.03 M A queous NaCl S olution

Aqueous 0.05 M SDS solution

Experimental CMC of SDS (mol/L)

15

Literature Value of CMC of SDS* (mol/L)

% Error


Without electrolyte (Pure Water)

1.1560 × 10−

8.0000× 10−

85.73

With electrolyte (0.02 M NaCl)

8.4100 ×10−

3.8200× 10−

77.98

*Source: Page 360 P of Principles of Colloid and Surface Chemistry by Hiemenz and Rajagopalan. CRC Press. 2017

From the table above, comparing the obtained CMC values, the CMC of SDS in NaCl solution is lower than the CMC of SDS in pure water. Thus, the presence of an electrolyte in a solution lowers the CMC of the surfactant. The addition of salt in surfactant solution is a way of reducing the CMC of a surfactant because the repulsive forces between the head groups of ionic surfactants are fighting against it aggregation which implies that the repulsive forces of head groups of SDS decreases due to the electrostatic shielding effect resulting in formation of micelle at a lower CMC. Ions of salts normally assist micelle formation, and help to formally bind the counter ions, increase the micelle aggregation number — description of the number of molecules present in a micelle once the critical micelle concentration (CMC) has been reached, affect the electrokinetic potential (zeta potential), and as well inﬂuence the energetics of the process (Naskar, et al., 2013). However, large errors that may have resulted in the determination of critical micelle concentration of SDS in different solutions may be due to the degradation of instrument and temperature fluctuations. The cell constant of conductivity meter was determined to be only 0.431 it should be between 0.71

− to

1.50

− .

−

when

Secondly, a constant temperature was not

maintained rather an increase in temperature was maintained. In general, repulsive forces between the head groups of ionic surfactants are fighting against the aggregation. This is due mainly to the decrease in the thickness of the ionic atmosphere surrounding the ionic head groups in the presence of the electrolyte and the consequent decreased electrical repulsion between them in the micelle. A decrease in the electrical repulsion would then mean a faster aggregation of monomers into micelles due to lesser resistance, thus a lower critical micelle concentration is obtained (Rosen & Kunjappu 2012). 16


The depression of the CMC Below CMC, no micelles are formed and the conductivity is due to the separate contributions of the dissociated ionic surfactants and of the free counterions. Also, an ionic surfactant is completely dissociated and there is a linear relationship between the molar conductivity, κ of the surfactant solution and its concentration as the surfactant monomers behave as normal electrolytes and thus obeying Kohlrausch’s Law of Independent Ion Migration,

 = [](  )

Equation 1

 is the conductivity, [] is the amphiphile (surfactant) concentration below CMC, and  and  are the molar ionic conductivities of the counterion and of the amphiphile, where

respectively. Kohlrausch’s Law of Independent Ion Migration states that every ion con tributes a definite amount to the equivalent conductance of an electrolyte in the limit of infinite dilution, regardless of the presence of other ions (Parker, 2003). Above the CMC,

κ

is constant and independent of surfactant concentration as micelles

behave like weak electrolyte. The addition of surfactant molecules increases the concentration of micelles, while the equilibrium monomer concentration remains constant. In this region, the conductivity again increases linearly with surfactant concentration, but due to the reduced ionic mobility of micelles compared to that of the monomers — the slope of this linear trend is smaller than that below the CMC. The conductivity above the CMC is the sum of four different contributions: the ionic conductivity of the counterion and of the amphiphile at the CMC, the micelle conductivity and the conductivity of the unbonded counterions from the micelles. The following equation applies: Equation 2 =(  )  [] ∝ ([ ] ) where ∝ is the dissociation degree and [] is the molar concentration of the micelles. If  is the average aggregation number, then [] = ([] — )/ , and assuming that the micelle 17


conductivity is the sum of the conductivity of all the charged monomers in the micelle, that is,

 =∝, equation 2 can be rearranged as follows. =(  )(1∝)∝(   )[]    has been obtained for concentrations below the CMC — the micelle ionization degree ∝ (Garti, & Then the slope of the trendline of the conductivity above the CMC provides — once

Amar-Yuli, 2012) A plot of molar conductivity of the surfactant versus the surfactant concentration gives a kink from which the CMC of the surfactant is obtained.

Fi g ure 8. Molar C onductivity of the S urfactant vs. the S urfactant Concentration

Post-Lab Questions 1. Assume that the cavity of SDS micelle has a diameter of 3nm and that it contains dissolved benzene molecules. What is the concentration of benzene in that micelle?

 = /  = 3 , = 1.5  = 1.5  10− 18


 = 43   = 43 (1.510− )  = 1.4136 × 10−  =1.4136×10−  −  3  × 6.02×101  =4.9834×10  −  4.9834×10  = 1.4136×10−  = 0.3 5  5. Conclusions The CMC of sodium dodecyl sulfate can be investigated via conductimetric techniques. In this experiment, the critical micelle concentration (CMC) of sodium dodecyl sulfate was determined by plotting conductivity as a function of concentration and extrapolating the results at low and high concentrations to an intersection point. That is, at the said point shows a significant change of a physico-chemical parameter which is conductivity. The experimental critical micelle concentration of aqueous sodium dodecyl sulfate solution in pure water at T = 30.0 °C and 400 RPM, is 1.1560 mmol/L. The 85.73 % error compared to the literature value which is 8.0 mmol/L is due to the errors in the experiment such as the fluctuating temperature during the experiment and due to instrumental errors. The critical micelle concentration of aqueous SDS solution in a 0.02 M NaCl solution is 0.8410 mmol/L. This shows that the addition of a dilute electrolyte solution decreases the critical micelle concentration.

19


References

Demissie, H., & Duraisamy, R. (n.d.). Effects of Electrolytes on the Surface and Micellar Characteristics

of

Sodium

Dodecyl

Sulphate

Surfactant

Solution .

doi:http://www.jsirjournal.com/Vol5_Issue6_03.pdf Naskar, B., Dey, A., & Moulik, S. P. (2013). Counter-ion Effect on Micellization of Ionic Surfactants: A Comprehensive Understanding with Two Representatives, Sodium Dodecyl Sulfate (SDS) and Dodecyltrimethylammonium Bromide (DTAB) . Journal of Surfactants and Detergents, 16(5), 785-794. doi:10.1007/s11743-013-1449-1 Garti, N., & Amar-Yuli, I. (2012). Nanotechnologies for Solubilization and Delivery in Foods and Cosmetics Pharmaceuticals. Lancaster, PA: DEStech Publications. Parker, S. P. (2003). The McGraw-Hill Dictionary of Scientific and Technical Terms. New York:

McGraw-Hill

Professional.

doi:https://books.google.com.ph/books?id=xOPzO5HVFfEC&pg=PA1158&dq Khan, M. N. (2007). Micellar C atalys is . Boca Raton, Fl: CRC/Taylor & Francis. Bucak, S., & Rende, D. (2014 ). Colloid and Surface Chemistry a Laboratory Guide for Exploration of the Nano World. Boca Raton, Fla.: CRC Press.

Atkins, P., de Paula, J. (2010). Atkins’ Physical Chemistry. 9th ed. Oxford: Oxford University Press.

20


ANNEX Data Processing & Analysis Report Cell constant:

0.431

Temperature (°C):

30

RPM:

400

Distilled water



0.05

 

0.3

[mol/L] [mL]

Measurement of Conductivity and determination of CMC of aqueous SDS solution Time (min)

Tempera ture

Volume Added (mL)

Total Volume of Solution (mL)

Conductivit y k [μS/cm]

Mol SDS (moles)

0

29.9

0.0

70.0

39.20

1

29.9

0.3

70.3

2

29.9

0.6

3

29.9

4



()



[mol/L]1/2

k/C [μS-L/cmmol]

0.000000

0.0000000

0.00000

0.00

53.91

0.000015

0.0002134

0.01461

252658.20

70.6

68.21

0.000030

0.0004249

0.02061

160520.87

0.9

70.9

80.94

0.000045

0.0006347

0.02519

127525.47

29.9

1.2

71.2

94.31

0.000060

0.0008427

0.02903

111914.53

5

29.9

1.5

71.5

108.10

0.000075

0.0010490

0.03239

103055.33

6

29.9

1.8

71.8

122.1

0.000090

0.0012535

0.03540

97408.67

7

29.9

2.1

72.1

136.2

0.000105

0.0014563

0.03816

93524.00

8

29.9

2.4

72.4

150.4

0.000120

0.0016575

0.04071

90741.33

9

29.9

2.7

72.7

164.8

0.000135

0.0018569

0.04309

88747.85

10

29.9

3.0

73.0

179.2

0.000150

0.0020548

0.04533

87210.67

11

29.9

3.3

73.3

193.5

0.000165

0.0022510

0.04744

85960.91

12

29.9

3.6

73.6

207.0

0.000180

0.0024457

0.04945

84640.00

13

29.9

3.9

73.9

219.4

0.000195

0.0026387

0.05137

83146.97

14

29.9

4.2

74.2

231.6

0.000210

0.0028302

0.05320

81832.00

15

29.9

4.5

74.5

243.7

0.000225

0.0030201

0.05496

80691.78

16

29.9

5.0

75.0

255.8

0.000250

0.0033333

0.05774

76740.00

17

29.9

5.5

75.5

273.1

0.000275

0.0036424

0.06035

74978.36

18

29.9

6.0

76.0

288.7

0.000300

0.0039474

0.06283

73137.33

19

29.9

6.5

76.5

303.1

0.000325

0.0042484

0.06518

71345.08

20

29.9

7.0

77.0

317.5

0.000350

0.0045455

0.06742

69850.00

21

29.9

7.5

77.5

331.4

0.000375

0.0048387

0.06956

68489.33

22

29.9

8.0

78.0

344.5

0.000400

0.0051282

0.07161

67177.50

23

29.9

8.5

78.5

356.7

0.000425

0.0054140

0.07358

65884.59

24

30.0

9.0

79.0

369.4

0.000450

0.0056962

0.07547

64850.22

(℃)

21

[mol/L]


25

30.0

9.5

79.5

380.4

0.000475

0.0059748

0.07730

63666.95

26

30.0

10.0

80.0

392.3

0.000500

0.0062500

0.07906

62768.00

27

30.0

10.5

80.5

403.8

0.000525

0.0065217

0.08076

61916.00

28

30.0

11.0

81.0

414.3

0.000550

0.0067901

0.08240

61015.09

29

30.0

11.5

81.5

425.0

0.000575

0.0070552

0.08400

60239.13

30

30.0

12.0

82.0

434.7

0.000600

0.0073171

0.08554

59409.00

31

30.0

12.5

82.5

444.7

0.000625

0.0075758

0.08704

58700.40

32

29.9

13.0

83.0

453.9

0.000650

0.0078313

0.08849

57959.54

33

30.0

13.5

83.5

462.7

0.000675

0.0080838

0.08991

57237.70

34

14.0

84.0

472.0

0.000700

0.0083333

0.09129

56640.00

35

30.0 30.0

14.5

84.5

480.7

0.000725

0.0085799

0.09263

56026.41

36

30.0

15.0

85.0

489.5

0.000750

0.0088235

0.09393

55476.67

37

15.5

85.5

497.8

0.000775

0.0090643

0.09521

54918.58

38

30.0 30.0

16.0

86.0

505.9

0.000800

0.0093023

0.09645

54384.25

39

30.0

16.5

86.5

513.9

0.000825

0.0095376

0.09766

53881.64

40

17.0

87.0

521.5

0.000850

0.0097701

0.09884

53377.06

41

30.0 30.0

17.5

87.5

529.4

0.000875

0.0100000

0.10000

52940.00

42

30.0

18.0

88.0

536.4

0.000900

0.0102273

0.10113

52448.00

43

30.0 30.0

18.5

88.5

543.8

0.000925

0.0104520

0.10223

52028.43

19.0

89.0

551.0

0.000950

0.0106742

0.10332

51620.00

19.5

89.5

558.3

0.000975

0.0108939

0.10437

51249.08

46

30.0 30.1

20.0

90.0

565.5

0.001000

0.0111111

0.10541

50895.00

47

30.1

20.5

90.5

572.6

0.001025

0.0113260

0.10642

50556.39

48

30.1

21.0

91.0

579.3

0.001050

0.0115385

0.10742

50206.00

49

30.1 30.1

21.5

91.5

586.3

0.001075

0.0117486

0.10839

49903.67

22.0

92.0

593.1

0.001100

0.0119565

0.10935

49604.73

22.5

92.5

599.6

0.001125

0.0121622

0.11028

49300.44

52

30.1 30.1

23.0

93.0

606.1

0.001150

0.0123656

0.11120

49015.04

53

30.1

23.5

93.5

612.5

0.001175

0.0125668

0.11210

48739.36

54

24.0

94.0

618.7

0.001200

0.0127660

0.11299

48464.83

55

30.1 30.1

24.5

94.5

624.8

0.001225

0.0129630

0.11386

48198.86

56

30.0

25.0

95.0

630.7

0.001250

0.0131579

0.11471

47933.20

57

25.5

95.5

637.0

0.001275

0.0133508

0.11555

47712.55

58

30.1 30.1

26.0

96.0

643.0

0.001300

0.0135417

0.11637

47483.08

59

30.1

26.5

96.5

648.8

0.001325

0.0137306

0.11718

47252.23

60

27.0

97.0

654.5

0.001350

0.0139175

0.11797

47027.04

61

30.2 30.2

27.5

97.5

660.4

0.001375

0.0141026

0.11875

46828.36

62

30.2

28.0

98.0

666.1

0.001400

0.0142857

0.11952

46627.00

63

30.2

28.5

98.5

671.4

0.001425

0.0144670

0.12028

46409.05

44 45

50 51

22


Conductivity (  ) vs. concentration of SDS (C)

CMC Determination from the Plot of Conductivity vs Concentration of SDS in Pure Water at T=30.7 , 400 RPM

℃

23


Conductivity of solution per molarity of solution (  /C) vs. the square root of the SDS concentration (C 1/2 )

CMC Determination from the Plot of /C vs C1/2 of SDS in Pure Water at T= 30.7 RPM

Sample Calculation of Concentration of SDS

  (  ) 0.05  (0)      = = =0.00  70    ( )     0   (70) 0.05    (0.30  ) , = = 70   0.30       = 0.0002134     

 ()     0.0002134   (70.30 ) 0.05    (0.30  )   = = 70.30   0.30     = 0.0004249    ′

24

℃, 400


From Figure 3, inflection point is at Since

 = 4.8997 × 10−   .

    ≅ ,  = 4.8 997 × 10−   . /



 =3.40 ×10−     = 1.1560 × 10−   From Figure 6, 

Since

≅ ,  = 1 1.1560 × 10−  

Cell constant:

0.431

Temperature (°C):

30

RPM:

400

Distilled water



0.05

 

0.3

[mol/L] [mL]

Determination of C MC of aqueous SDS solution when added with 0.02M NaCl Mol SDS (moles)



k/C [μSL/cmmol]

Time (min)

Temperatur e

Volume Added (mL)

0

29.9

0.0

70.0

2314

0.000000

1

30.0

0.2

70.2

2316

0.000010

0.000142

0.01194

2

30.1

0.4

70.4

2319

0.000020

0.000284

0.01685

3

30.1

0.6

70.6

2321

0.000030

0.000425

0.02061

4

30.2

0.8

70.8

2322

0.000040

0.000565

0.02377

97689.72

5

30.2

1.0

71.0

2325

0.000050

0.000704

0.02654

87612.71

6

30.3

1.2

71.2

2326

0.000060

0.000843

0.02903

80126.11

7

30.3

1.4

71.4

2327

0.000070

0.000980

0.03131

74318.42

8

30.4

1.6

71.6

2328

0.000080

0.001117

0.03343

69645.73

9

30.4

1.8

71.8

2328

0.000090

0.001253

0.03540

65754.27

10

30.4

2.0

72.0

2329

0.000100

0.001389

0.03727

62493.63

11

30.4

2.2

72.2

2329

0.000110

0.001524

0.03903

59668.04

12

30.4

2.4

72.4

2330

0.000120

0.001657

0.04071

57231.43

13

30.4

2.6

72.6

2330

0.000130

0.001791

0.04232

55062.07

14

30.5

2.8

72.8

2330

0.000140

0.001923

0.04385

53132.17

15

30.5

3.0

73.0

2331

0.000150

0.002055

0.04533

51423.08

16

30.5

3.2

73.2

2330

0.000160

0.002186

0.04675

49836.95

(℃)

Conductivit y k [μS/cm]

()

Total Volume of Solution (mL)

25



[mol/L]

[mol/L]

1/2

194047.0 8 137585.3 1 112594.4 2


17

30.5

3.4

73.4

2330

0.000170

0.002316

0.04813

48414.95

18

30.5

3.6

73.6

2330

0.000180

0.002446

0.04945

47114.93

19

30.5

3.8

73.8

2329

0.000190

0.002575

0.05074

45900.86

20

30.5

4.0

74.0

2329

0.000200

0.002703

0.05199

44799.21

21

30.5

4.2

74.2

2329

0.000210

0.002830

0.05320

43778.59

22

30.5

4.4

74.4

2328

0.000220

0.002957

0.05438

42811.27

23

30.5

4.6

74.6

2328

0.000230

0.003083

0.05553

41926.49

24

30.4

4.8

74.8

2327

0.000240

0.003209

0.05664

41081.05

25

30.4

5.0

75.0

2326

0.000250

0.003333

0.05774

40287.50

26

30.4

5.2

75.2

2326

0.000260

0.003457

0.05880

39557.78

27

30.4

5.4

75.4

2325

0.000270

0.003581

0.05984

38853.20

28

30.4

5.6

75.6

2324

0.000280

0.003704

0.06086

38187.22

29

30.4

5.8

75.8

2323

0.000290

0.003826

0.06185

37556.47

30

30.4

6.0

76.0

2322

0.000300

0.003947

0.06283

36957.99

31

30.4

6.2

76.2

2321

0.000310

0.004068

0.06378

36389.14

32

30.4

6.4

76.4

2320

0.000320

0.004188

0.06472

35847.57

33

30.3

6.6

76.6

2319

0.000330

0.004308

0.06564

35331.18

34

30.3

6.8

76.8

2318

0.000340

0.004427

0.06654

34838.11

35

30.3

7.0

77.0

2317

0.000350

0.004545

0.06742

34366.66

36

30.3

7.2

77.2

2316

0.000360

0.004663

0.06829

33915.32

37

30.3

7.4

77.4

2316

0.000370

0.004780

0.06914

33497.17

38

30.3

7.6

77.6

2314

0.000380

0.004897

0.06998

33067.58

39

30.2

7.8

77.8

2313

0.000390

0.005013

0.07080

32668.80

40

30.2

8.0

78.0

2312

0.000400

0.005128

0.07161

32285.32

41

30.2

8.2

78.2

2311

0.000410

0.005243

0.07241

31916.22

42

30.2

8.4

78.4

2309

0.000420

0.005357

0.07319

31546.95

43

30.2

8.6

78.6

2308

0.000430

0.005471

0.07396

31204.19

44

30.2

8.8

78.8

2307

0.000440

0.005584

0.07472

30873.39

45

30.1

9.0

79.0

2306

0.000450

0.005696

0.07547

30553.90

46

30.1

9.2

79.2

2304

0.000460

0.005808

0.07621

30231.95

47

30.1

9.4

79.4

2303

0.000470

0.005919

0.07694

29933.35

48

30.1

9.6

79.6

2302

0.000480

0.006030

0.07765

29644.30

49

30.1

9.8

79.8

2302

0.000490

0.006140

0.07836

29377.09

50

30.1

10.0

80.0

2300

0.000500

0.006250

0.07906

29092.95

51

30.1

10.2

80.2

2299

0.000510

0.006359

0.07974

28829.76

52

30

10.4

80.4

2298

0.000520

0.006468

0.08042

28574.35

26




C MC D etermination from the Plot of /C v s / of S DS in 0.02 M Aqueous NaCl Solution at 30.3 , 400 rpm

 ℃

27

FLORES-CMC-ILAR-2017.docx

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