Thermodynamics of Sodium Dodecyl Sulfate (SDS) Micellization: An Undergraduate Laboratory Experiment

An undergraduate laboratory experiment is presented that allows a thermodynamic characterization of micelle formation of sodium dodecyl sulfate (SDS) in aqueous solutions. The critical micelle concentration (CMC) and the degree of micelle ionization (α) are obtained at different temperatures by cond...

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Bibliographic Details
Published in:Journal of chemical education 2011-05, Vol.88 (5), p.629-633
Main Authors: Marcolongo, Juan P, Mirenda, Martín
Format: Article
Language:English
Subjects:
Aqueous solutions
Chemical compounds
Chemical reactions
Chemistry
College Science
Computer mediated communication
Enthalpy
Entropy
Experiments
Free energy
Higher education
Ionization
Micelles
Molecular Structure
Science Experiments
Science Laboratories
Scientific Concepts
Sodium
Sodium dodecyl sulfate
Sulfates
Surfactants
Temperature
Thermodynamics
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Summary:An undergraduate laboratory experiment is presented that allows a thermodynamic characterization of micelle formation of sodium dodecyl sulfate (SDS) in aqueous solutions. The critical micelle concentration (CMC) and the degree of micelle ionization (α) are obtained at different temperatures by conductimetry. The molar standard free energy (Δmic G̅), enthalpy (Δmic H̅°), and entropy (Δmic S̅°) for the micellization process are calculated using the CMC, α, and their temperature dependences within the framework of a simplified model, the closed association model, which assumes an equilibrium between free surfactant monomers and monodispersed micelles. On the basis of hydration phenomena of surfactant molecules, a physicochemical discussion of the results is also proposed.
ISSN:0021-9584
1938-1328
DOI:10.1021/ed900019u