The value of the density of alcohols in 0.015M SDS+Ethanol decreases as the composition of the alcohols increases. Propanol, n-Butanol, n-Pentanol, iso-Propanol, iso-Butanol and iso-Pentanol in 0.015M SDS+Ethanol at a 0.2 mole fraction.
AG AGE
Properties of solutions
Therefore, theoretical treatments must assume a model (eg, network model, cell model, etc.) for the structure of the components and their solution. Solution theory is still far from being adequate to account for non-ideal solutions in terms of the properties of the constituent molecules.
Properties of alcohols
The oxygen atom of an alcohol's highly polarized 0-H bond pulls the electron density away from the hydrogen atom. Alcohols with five or more carbon atoms (Pentanol and higher) are effectively insoluble in water due to the dominance of the hydrocarbon chain.
Surfactants
Two opposing solubility trends in alcohols are: the tendency of the polar -OH to favor solubility in water, and the tendency of the carbon chain to oppose it. Methanol, ethanol and n-propanol are therefore miscible with water because the hydroxyl group wins over the short carbon chain.
Classification of surfactants
It may be mentioned that the self-aggregation of surfactant molecules in water/oil arises due to the dual affinity of these molecules for water and oil.
Physical Properties of Surfactant Solutions
The reduction of the Gibbs free energy of the system, which is the result of the preferential self-association of the hydrophobic hydrocarbon chain of monomeric surfactant molecules, is the main reason for the formation of a micelle. The large positive entropy change in micelle formation is due to the breakdown of the water structure around the hydrocarbon part of the monomeric surfactant species.
Alcohol SDS interactions
Blends containing oxygenated compounds such as alkanols are also important materials in the petroleum industry due to their use in gasoline octane enhancement as additives and pollution reduction properties. Because blends of ethanol with alkanols can be used as oxygenates in fuels and blends containing oxygen compounds are also important materials in the petroleum industry due to their use in increasing the octane number of gasoline as additives.
The object of the present work
In view of this, we carried out the volumetric, viscometric and thermodynamic studies of surfactants (used as stabilizer) containing ethanol with isomeric alkanols in terms of interactions with dissolved solvents. The knowledge of the main factors involved in the non-ideality of liquid mixtures is fundamental for a better understanding of excess molar volumes and excess viscosities.
Physical Properties and Chemical Constitutions
A colligative property is one that depends primarily on the number of molecules involved and not on their nature and size. Such properties are the lowering of the vapor pressure, the raising of the boiling point, the lowering of the freezing point and the osmotic pressure of dilute solutions upon the addition of non-volatile solute molecules.
Density
Density and Temperature
If n2 is the number of moles of solute and V liter is the volume of the solution then,. M2 = Molecular weight of solute in grams V1 = Volume of solvent in ml. Po = Density of solvent in g cm'.
Apparent! Partial Molar Volume
If 'Y' represents the partial molarity of a binary solution at constant temperature and pressure, Y will then be a function of two independent variables n1 and n2, which represent the number of moles of the two components present. The usefulness of the concept of partial molar properties lies in the fact that it can be expressed mathematically as,
Excess Molar Volume
By putting the value of and of the experimental liquid/solution and the value of viscornet constant A in equation (2.27), the viscosity coefficient can be obtained for a liquid at a certain temperature. At elevated temperatures, the kinetic energy of the molecules increases at the expense of intermolecular forces, which gradually decrease.
Excess Viscosity Measurements
Water and alcohol mixture shows this type of behavior probably due to H-bond formation between water and alcohol molecules. 41 values indicate the decrease in association of associated liquids (H-bonded) or increase in the internuclear distance between them.
Interaction Parameter Measurements (E)
Viscosity as a Rate Process
- Enthalpy (AH) and Entropy (tS) of activation for viscous flow
The jump of moving molecules from one equilibrium position to another can thus be regarded as equivalent to the passage of the system across the plane of the energy barrier. For example, in ordinary liquids, the activation step may be the creation of voids or holes in the body of the liquid into which a neighboring molecule can move.
Different Thermodynamic Parameters
- Change of free energy of activation (AG') for viscous flow
- Change of enthalpy of activation (AH*) for viscous flow
AS = - intercept x R ..(2.47) AH' and AS' are respectively the activation enthalpy per mole for viscous flow and AS' is the activation entropy. In view of the high activation energy for the flow of associated fluids, it is a striking fact that the free activation energy does not show such a deviation.
Redlich-Kister Equation
The explanation is that AG corresponds to (AH5 - TAS) and that the high value of the activation enthalpy AH5 is compensated by the large positive value of AS5, so that AG5 remains normal. In other words, the entropy of activation AS5 for flow should be relatively large positive, consistent with the experimental fact that AGt is normal despite the volume of AH5 for associated fluids.
General Techniques
Materials
Preparation and Purification of Solvent
Apparatus
Methods (preparation of solution)
Conductance measurements
Density measurements
The density bottle was carefully clamped with a stand in the thermostatic water bath maintained at the desired temperature. The difference between the two weights (weight with solution and without solution) gave the weight of the solution in the density bottle.
Excess molar volume measurements
As the solution began to warm to the temperature of the bath, excess liquid overflowed through the capillary. The interior of the viscometer was thoroughly cleaned with hot chromic acid and then with distilled water so that there was. The viscometer was then clamped vertically in the thermostatic water bath so that the top mark on the top bulb was well below the water level.
With the aid of the pipette filler attached to the narrower limb of the viscometer, water was drawn above the upper mark of the bulb.
Excess viscosity measurements
The water from the bulb was then allowed to fall into the capillary and the time of the drop between the two marks was recorded using a stopwatch reading to 0.01 second. To check the reproducibility of the flow time, the reading at each temperature was repeated three or four times, keeping the temperature at the same value. Since the accurate viscosity and density of water at different temperatures are known (from literature), the calibration constant A of the viscometer for different temperatures was obtained using Eq.
By adding the values of the calibration constant, density, and flow time of the experimental solution, the viscosity of this solution was determined using Equation 3.40.
Interaction parameter measurements
Thermodynamic parametes
The excess enthalpy of activation, AH*, excess entropy of activation, AS*, and excess free energy of activation, L\G* have been calculated as -.
Coefficient Redlich-Kister equation and standard deviation
The CMC of sodium dodecyl sulfate (SDS) in ethanol was determined from the conductance, density, and viscosity measurements. The concentration dependence of molar conductivity of SDS in ethanol data is shown in Figure 4.3. The estimated value of CMC was found to be 0.0 15 mol.L* The conductance data are in good agreement with the viscosity and density data.
The effect of surfactant (SDS) on the ethanol-to-alcohol system has been studied in terms of measuring volumetric, viscometric and thermodynamic properties.
Volumetric properties
The effect of temperature on yE shows a definite trend, that is, the VE values increase with the increase in temperature. These factors may be primarily responsible for the resulting positive excess molar volume of the mixtures of 0.015M SDS+ Ethanol + Alkanols. The increase of VE with the carbon chain length of alcohols may be related to the increase in the size of alcohols.
Therefore, due to its hydrophilic effect, it has the possibility of forming hydrogen bonds through the polar group of alkanols and 0.015M SDS+ethanol.
Viscometric properties
- Interaction parameter
The dependence of viscosity and carbon chain length of alcohols of different composition at a fixed temperature are plotted in Figures 4.55-4.60. The dependence of viscosity on the number of carbon atoms of alcohols at different temperatures at fixed composition are plotted in Figures 4.61-4.64. After reaching the state of minima 17E, further addition of alcohol continuously formed the ordered structure and the alkanols-alkanols-cage association, instead of the SDS-alkanols dispersion, resulting in the continuous increase of 17E •. The dependence of the excess viscosity on the number of carbon atoms of alcohols of different composition at a fixed temperature are plotted in figure. The dependences of excess viscosity on the number of carbon atoms of alcohols of different temperatures at fixed composition are plotted in Figures 4.82-4.84.
The negative excess viscosities are accounted for due to the dissociation of the associated structures of alcohols in SDS + Ethanol.
Thermodynamic properties
The values of the built-in parameters together with the standard deviation of alcohol systems are presented in table 4.31. This is of course expected given the branching of the hydrocarbon moieties in the isomeric alkanols. This also attributes that the structural factor dominates the international one, as in the case of mixing properties.
An investigation of the AFt values of the alcohols shows that the AFt of iso-Butanol is higher than that of the other 1- alcohol systems studied.
0.015M SDS+Ethanol
0.015M SDS+Ethano1
Results and Discussion Cl: Chapter IV Table 4.30: The coefficient, a, of the Redlich-Kister equation expressing it and the standard deviation, cy for n-propanol, n-butanol, n-pentanol, iso-propanol, iso-butanol and iso - Propanol +0.015 M.
MINA
Liii
KIPA
0.3 Results and Discussion
290 Results and Discussion
IiII
The values of the excess viscosity, r/ turn out to be negative, indicating that the 0.015 M SDS + Ethanol solutions of the alcohols are not ideal. Positive, negative and negative YE and for the studied alcohol systems 0.015 M SDS+Ethariol + show agreement with the statements. With the addition of alkanols to the 0.015 M SDS+Ethanol solution, strong dissociative forces appear and the H bond in the alkanols dissociates causing volume expansion.
For n-Propanol, iso-Propanol, n-Butanol, iso-Butanol, n-Pentanol and iso-Pentanol in 0.015M SDS+Ethanol systems, AG are negative over the entire composition range.
