The author is very grateful to the Almighty God for the successful completion of the research work and the preparation of this thesis. The observed values of VE for the mixtures have been explained in terms of physical, chemical and geometrical contributions.
Properties of solutions
The theoretical treatments must therefore assume some model (eg lattice model, cell model etc.) for the structure of the components and their solution. Some of the usually experimentally determined macroscopic properties are: density, viscosity, thermodynamic properties, surface tension, etc., which are easily measurable.
Physical properties of alcohols
Alcohols are strongly polar, so they are better solvents than alkanes for ionic and polar compounds. Binary and ternary mixtures of alcohols are interesting because of the self-assembly of similar molecules and the ability to form intermolecular hydrogen.
Surfactants
Classification of surfactants
Physical Properties of Surfactant Solutions
The decrease in the Gibbs free energy of the system, which is due to the preferential self-association of the hydrophobic hydrocarbon chain of monomeric surfactant molecules, is the primary reason for the formation of micelles. Two main approaches, namely the phase separation model and the mass separation model for the thermodynamic analysis of the micellization process, have gained wide acceptance.
Factors affecting critical micelle concentrations
The pronounced changes are influenced by those molecules (e.g., medium chain alcohols) that may be located in the outer regions of the micelle. Micelles containing more than one surfactant often form readily with a CMC lower than that of the pure components.
Structure of micelle
Critical micelle concentrations depend almost entirely on the nature of the lyophobic moiety of the surfactant. The nature of water's atomic structure causes its molecules to have unique electrochemical properties.
Structure of water
The expansion of the water molecule during freezing allows the ice to float on liquid water. The introduction of a solute into liquid water causes changes in the properties of the solvent similar to those caused by temperature or pressure.
![Fig 1.4: Frank and Wen model for the structure modification produce by an ion The hydrogen bonding in the clusters is postulated to be cooperative phenomenon [29]](https://thumb-ap.123doks.com/thumbv2/filepdfnet/10925902.0/49.893.187.747.154.601/structure-modification-produce-hydrogen-clusters-postulated-cooperative-phenomenon.webp)
Hydrophilic hydration
The thermodynamic and transport properties are sensitive to the interactions between solute and solvent, solute and solvent. The concentration dependences of the thermodynamic properties are a measure of solute–solute interaction, and in the limit of infinite dilutions, these parameters serve as a measure of solute–solvent interactions.
Hydrophobic hydration and hydrophobic interaction
The experimental result on various macroscopic properties provides useful information for a proper understanding of the specific interactions between the components and the structure of the solution. Because hydrophobic hydration plays an important role in promoting amphiphiles to aggregate in bulk water and in superabsorption at the aqueous-air interface, a constant goal of chemists working in these areas has been to seek a clearer understanding of the molecular nature behind the subtle phenomenon of hydration between nonpolar solutes. and water.
Properties of Acetonitrile
The mode of interaction between alcohols and acetonitrile is of vital importance in the field of solution chemistry because it can provide important information about hydrophilic and hydrophobic interactions. Acetonitriles and alcohols are versatile solvents used in the separation of saturated and unsaturated hydrocarbons, in pharmaceutical synthesis, and serve as solvents for many polymers.
Acetonitrile-Solvent systems
The densities and viscosities of butanenitrile + 1-butanol, + 2- methyl-1-propanol, + 2-butanol or + 2-methyl-2-propanol were measured at several temperatures [50]. The vapor pressure of butanenitrile + 2-methyl-1-propanol or + 2-methyl-2-propanol at several temperatures has been reported [53].
The object of the present work
Excess Gibbs free energy, excess enthalpies and volumes were also measured for butane nitrile + 2-butanol, 2-methyl-1-propanol and 2-methyl-2-propanol [48]. Excess molar enthalpies and volumes of butane nitrile +2-methyl-1-propanol or +2-methyl-2-propanol at different temperatures were also measured [51].
Physical Properties and chemical constitutions
An additional property is one that, for a given system, is the sum of the corresponding properties of the constituents. There are other molecular properties such as molar volume, radioactivity, etc. that are highly additive in nature. ii) Purely Constitutive Properties: A property which depends entirely on the arrangement of atoms in a molecule and not on their number is called a purely constitutive property.
Density
The relative density of a substance is the ratio between the weight of a given volume of the substance and the weight of an equal volume of water at the same temperature (d104). The density of a liquid can be determined by weighing a known volume of the liquid in a density flask or picnometer, or by a flotation method based on Archimedes' principle.
Density and temperature
25. at 40C), the density of water at this temperature in gmL-1 is unity and the density of water at any other temperature is expressed relative to that of water at 40C and is expressed by (d104). The absolute temperature density of a given substance t0C is equal to the relative density multiplied by the density of water at the temperature.
Molarity
In our current investigation, the density of the pure components and the mixture was determined by weighing a specific volume of the liquid in question in a density bottle.
Molar volume of Mixtures
The positive deviation in volume, i.e. volume expansion, is explained by the breakdown of the association mode by H-bonding of the associated liquids. Many observers have thought that the negative deviation in the molar volume, i.e. volume contraction, arises from the i) formation of bonds by association, ii) decrease in the intermolecular distance between the interacting molecules, iii) interstitial accommodation of smaller species in the structural structure. network of the larger species and (iv) change in the bulk structure of any of the substances forming the mixture.
Excess molar volume
When two components are mixed together, there can be a positive or negative deviation in volume.
Viscosity
The driving pressure P = hρg, where h is the difference in height of the surface of the two reservoirs, since the external pressure is the same at the surface of both reservoirs, g = acceleration due to gravity and ρ = the density of liquid. By putting the value of and of the experimental liquid/solution and the value of viscometer constant A into equation (2.33), the viscosity coefficient for a liquid at a given temperature can be obtained.
Viscosity and temperature
At high temperatures, the kinetic energy of molecules increases at the expense of intermolecular forces, which decrease progressively. Viscosity also depends on pressure, molecular weight or mass of the molecule, molecular size and especially chain length, magnitude of intermolecular forces, such as association in pure liquids.
Viscosity of liquid mixtures
Therefore, the molecules of a liquid at high temperature offer less resistance to the flow and therefore less viscosity. Again, this type of behavior can also arise from the entrapment of smaller molecules in the matrices of larger species.
Excess viscosity measurements
Water and alcohol mixture exhibits this type of behavior probably as a result of H-bond formation between water and alcohol molecules. The negative deviation of viscosities, i.e. lower viscosities than the ideal values indicate the decrease in association of associated liquids (H-bonded) or the increase in the internuclear distance between them.
Interaction parameter measurements, (ε)
Viscosity as a rate process
To treat the viscosity of a fluid as a rate process, it is assumed that.. i) The motion of one layer relative to another is assumed to involve the passage of a molecule from one equilibrium position to another is the same layer. ii). The jump of the moving molecules from one equilibrium position to the next can thus be considered equivalent to the passage of the system over a plot of energy barrier.
Different thermodynamic parameters
- Free energy of activation (ΔG # ) for viscous flow
- Enthalpy of activation (ΔH # ) for viscous flow
- Entropy of activation (ΔS # ) for viscous flow
If, as suggested above, the unit of even in associated liquids is a single molecule and the formation of the activated state involves a number of hydrogen bonds, it is clear that the entropy of the activated state will be considerably greater than that of the initial status. stands. In other words, the entropy of activation AS# for flow should be relatively large positive, consistent with the experimental fact that AG# is normal despite the volume of the ΔH# for associated fluids.
Redlich-Kister equation
All the calculated excess properties, their corresponding polynomial coefficients and the standard deviation values are shown in the tables. In the figures, solid lines are drawn using the calculated excess property values using a computer program; whereas the symbols represent the corresponding experimental excess property values.
General Techniques
Materials
Preparation and Purification of Solvent
The glassware used for measuring the density of solvents and solutions was from the density bottle. Both the density bottle and viscometer were calibrated with double distilled water at the studied temperature.
Methods (preparation of solution)
The flow time of liquids was recorded by a stopwatch that could read up to 0.01 seconds.
Conductance measurements
Density measurements
The density bottle is carefully clamped with stand in the thermostatic water bath which is 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
The density bottle was first thoroughly cleaned with hot chromic acid and then with sufficient distilled water. When no overflow was observed through the capillary, the density bottle was removed from the thermostatic water bath, wiped with tissue paper, dried and weighed in the analytical balance.
Viscosity measurements
X2, M2 and 2 are the corresponding values of component 2 (organic solution); and mix is the density of the mixture. 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.
Excess viscosity measurements
Interaction parameter measurements
Interaction parameter, ε is usually considered as an approximate measure of the strength of the interactions between components. The negative value of η indicates that there is no specific interaction between the components present in the mixture and the positive value of η indicates the presence of strong interaction.
Thermodynamic parameters
The excess enthalpy of activation, ΔH#, excess entropy of activation, ΔS# and excess free energy of activation, ΔG# have been calculated as-.
Coefficient Redlich-Kister equation and standard deviation
Where PROPE represents any excess property (excess molar volume or excess viscosity etc.) for a binary liquid mixture composition and X1 is the corresponding mole fraction of component one. Solid lines have been drawn in the figures using the surplus value of real estate calculated using a computer program; while the symbols represent the corresponding experimental redundant feature values.
Conductance and viscosity studies of SDS
From these studies we obtained various information which are presented and discussed in various sections in the light of theories mentioned in the previous chapter. It shows a sharp break in its value where micelles start to form and it is determined by extrapolating the molar conductivity data in the pre-micelle region to intersect with a straight line drawn through the data in the post-micelle region.
Volumetric Properties
From the figures it can be seen that at the same temperature the density increases with the carbon chain length of the alcohols. For all the systems d VE/dT is negative. iv) The effect of temperature on VE shows a clear trend, i.e. The VE values increase with the increase in temperature.
Viscometric properties
- Interaction parameter
The values of the fitted parameters together with the standard deviation are shown in Tables 4.33. The variation of ηE with respect to the mole fraction of alcohol (X2) is shown in Figures 4.82-4.88 respectively. The negative excess viscosities are caused by the dissociation of the associated structures of alcohols in (80% acetonitrile + 20% water + 0.02 M SDS).
Thermodynamic properties
The values of the fitted parameters along with the standard deviation of alcohol systems are shown in Table 4.34. The ΔG#E values are negative in magnitude, indicating that ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol in (80% acetonitrile + 20% water + 0.02 M SDS) solutions are not ideal. Excess free energy ΔG#E is negative at all temperatures over the entire composition range for ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol in (80% acetonitrile + 20% water + 0.02M SDS) systems with .
