Greetings,
I have a problem regarding equation Gibb energy for micellization.
Through a reference from ( Zana, R. (1996). Critical micellization concentration of surfactants in aqueous solution and free energy of micellization. Langmuir, 12(5), 1208-1211), They showed many types of equation can be used with specific paramaters.
Unfortunately, may I know how exactly to perform the calculation?
Let's say I have this equation.
G= RT ln CMC
R is 8.3145 J/mol K , T is absolute temperature (K), CMC is critical micellar aggregation
If SDS surfactant has cmc of 8.2 mM, in 25 degree celsius (25 + 273 = 298K) R=8.3145 J/mol K,
Is it the Gibbs is -22.0 kJ/mol???
This is from wikipedia. https://en.wikipedia.org/wiki/Thermodynamics_of_micellization
Do we simply calculate using calculator???
Hope anybody can help me.
For non-ionic surfactant, use the equation delta G= RT ln CMC.
For ionic surfactants (SDS) it is necessary for phase-separation model
delta G= 2RT ln CMC.
For mass-action model it is necessary to make a correction for the ionization of the micelles to introduce the degrees of dissociation of micelles of alpha
delta G= (2- alpha) RT ln CMC.
Numerically, two values differ, because the calculation of the mole fraction differs. In modern articles, the degree of dissociation of micelles is necessarily used. See Chem.Soc.Revs. 1977. 6. 1. 25-42.
Yuri Mirgorod , thus for the SDS calculation, should be the delta G=2RT ln CMC , in which we have delta G= 2*8.3145*298*ln 8.2x10-3, equal to -23.80 kJ/mol. Right?
@yuri how about equation with delta G= (2-beta) RTln cmc and also another equation with delta G=(1+beta) RT ln cmc.
I confused about this equation
deltaG= (1+m/n)RTlnCMC, deltaG=(2-alpha)RT lnCMC,
alpha+m/n =1. Two identical equations. m/n - fraction of the charge of the surfactant ions in each micelle is neutralized. n—number surfactant ions RSO4-, m – number firmly bound counter ions Na+.
Yuri Mirgorod , can my degree of dissociation above 1? and is it all equations above consider as gibbs adsorption ?
@Nurul Faiezin Zul
It is not necessary for me to ask what is the degree of dissociation, but to read in books. I'm not a school teacher. Last time I answer your questions. NaCl is a strong electrolyte. It dissociates completely into ions. Therefore, its degree of dissociation is equal to 100% or 1. CH3COOH is weak electrolyte dissociates partially. Therefore, the degree of dissociation is less than 1. The Gibbs adsorption is calculated by the Gibbs equation of adsorbtion..We discussed the Gibbs energy of the surfactant micelle formation, and not adsorption.
Yuri Mirgorod ,
Thank you very much Prof Yuri. I really appreciate your replied.
I'm sorry if I ask so many questions regarding the Gibbs.
Degree of dissociation is always less than 1.
Alpha = post micellization slope/ pre micellization slope.
And if it is more than or equal to 1 then the plot between specific conductance vs. ads concentration will be A straight line and it will be very difficult for you to estimate CMC.
The so-called "entropy " doesn't exist at all.
During the process of deriving the so-called entropy, in fact, ΔQ/T can not be turned into dQ/T. That is, the so-called "entropy " doesn't exist at all.
The so-called entropy was such a concept that was derived by mistake in history.
It is well known that calculus has a definition,
any theory should follow the same principle of calculus; thermodynamics, of course, is no exception, for there's no other calculus at all, this is common sense.
Based on the definition of calculus, we know:
to the definite integral ∫T f(T)dQ, only when Q=F(T), ∫T f(T)dQ=∫T f(T)dF(T) is meaningful.
As long as Q is not a single-valued function of T, namely, Q=F( T, X, …), then,
∫T f(T)dQ=∫T f(T)dF(T, X, …) is meaningless.
1) Now, on the one hand, we all know that Q is not a single-valued function of T, this alone is enough to determine that the definite integral ∫T f(T)dQ=∫T 1/TdQ is meaningless.
2) On the other hand, In fact, Q=f(P, V, T), then
∫T 1/TdQ = ∫T 1/Tdf(T, V, P)= ∫T dF(T, V, P) is certainly meaningless. ( in ∫T , T is subscript ).
We know that dQ/T is used for the definite integral ∫T 1/TdQ, while ∫T 1/TdQ is meaningless, so, ΔQ/T can not be turned into dQ/T at all.
that is, the so-called "entropy " doesn't exist at all.
.
.
.
Why did the wrong "entropy" appear ?
In summary , this was due to the following two reasons:
1) Physically, people didn't know Q=f(P, V, T).
2) Mathematically, people didn't know AΔB couldn‘t become AdB directely .
If people knew any one of them, the mistake of entropy would not happen in history.
Please read my paper and those answers of the questions related to my paper in my Projects.
https://www.researchgate.net/publication/230554936_Entropy_A_concept_that_is_not_a_physical_quantity
1. Logic of the Second Law of Thermodynamics: Subjectivism, Logical Jump, Interdisciplinary Argumentation.
2. New thermodynamics pursues universality, two theoretical cornerstones:
2.1 Boltzmann formula: ro=A*exp(-Mgh/RT) - Isotope centrifugal separation experiments show that it is suitable for gases and liquids.
2.2. Hydrostatic equilibrium: applicable to gases and liquids.
3. The second and third sonic virial coefficients of R143a derived from the new thermodynamics are in agreement with the experimental results.
3.1. The third velocity Virial coefficient derived is in agreement with the experimental data, which shows that the theory is still correct when the critical density is reached.
4. See Appendix Pictures and Documents for details.
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