Solutions osmotic properties

We shall be interested in determining the effect of electrolytes of low molecular weight on the osmotic properties of these polymer solutions. To further simplify the discussion, we shall not attempt to formulate the relationships of this section in general terms for electrolytes of different charge types-2 l, 2 2, 3 1, 3 2, and so on-but shall consider the added electrolyte to be of the 1 1 type. We also assume that these electrolytes have no effect on the state of charge of the polymer itself that is, for a polymer such as, say, poly (vinyl pyridine) in aqueous HCl or NaOH, the state of charge would depend on the pH through the water equilibrium and the reaction... 

It is important to realise that whilst complete dissociation occurs with strong electrolytes in aqueous solution, this does not mean that the effective concentrations of the ions are identical with their molar concentrations in any solution of the electrolyte if this were the case the variation of the osmotic properties of the solution with dilution could not be accounted for. The variation of colligative, e.g. osmotic, properties with dilution is ascribed to changes in the activity of the ions these are dependent upon the electrical forces between the ions. Expressions for the variations of the activity or of related quantities, applicable to dilute solutions, have also been deduced by the Debye-Hiickel theory. Further consideration of the concept of activity follows in Section 2.5. 

Chapters 7 to 9 apply the thermodynamic relationships to mixtures, to phase equilibria, and to chemical equilibrium. In Chapter 7, both nonelectrolyte and electrolyte solutions are described, including the properties of ideal mixtures. The Debye-Hiickel theory is developed and applied to the electrolyte solutions. Thermal properties and osmotic pressure are also described. In Chapter 8, the principles of phase equilibria of pure substances and of mixtures are presented. The phase rule, Clapeyron equation, and phase diagrams are used extensively in the description of representative systems. Chapter 9 uses thermodynamics to describe chemical equilibrium. The equilibrium constant and its relationship to pressure, temperature, and activity is developed, as are the basic equations that apply to electrochemical cells. Examples are given that demonstrate the use of thermodynamics in predicting equilibrium conditions and cell voltages. 

To eliminate the threat of shock, replenishment of the circulation is essential. With moderate loss of blood, administration of a plasma volume expander may be sufficient Blood plasma consists basically of water, electrolytes, and plasma proteins. However, a plasma substitute need not contain plasma proteins. These can be suitably replaced with macromolecules ( colloids ) that like plasma proteins, (1) do not readily leave the circulation and are poorly filtrable in the renal glomerulus and (2) bind water along with its solutes due to their colloid osmotic properties. In this manner, they will maintain circulatory filling pressure for many hours. On the other hand, volume substitution is only transiently needed and therefore complete elimination of these colloids from the body is clearly desirable. 

At this point the system is finally ready to stick a knife in the invader. One of the pieces of C5 sticks to C6 and C7. This structure has the remarkable property of being able to insert itself into a cell membrane. C5b,6,7 then binds to a molecule of C8 and a variable number (from one to eighteen) of molecules of C9 adds to it. The proteins, however, do not form an undifferentiated glob. Rather, they organize themselves into a tubular form that punches a hole in the membrane of the invading bacterial cell. Because the insides of cells are very concentrated solutions, osmotic pressure causes water to rush in. The in-rushing water swells the bacterial cell till it bursts. 

Real colligative properties are only found in ideal gases and ideal solutions. Examples are osmotic pressure, vapour pressure reduction, boiling-point elevation, freezing-point depression, in other words the osmotic properties. 

The information in this section was taken fiiom Physiccd Chemistry by Castellan [21]. In a solution where the solute is not volatile (e.g., salts, polymers, and surfactants), the vapor pressure of the solvent is limited by the mole fraction of the solvent at the interface. Several other solution properties are also dependent on the mole fraction of the solute, x, only and not on the chemical nature of the solute. These properties are referred to as coUigative properties (fram the latin Un-gare, to bind, and co, together which include vapor pressure lowering, frezing point depression, boiling point elevation, and osmotic pressure. In each case, two phases are in equilibrium—one of which is the solution. 

This is used to express the concentration of solute relative to the mass of solvent, i.e. molkg . Molality is a temperature-independent means of expressing solute concentration, rarely used except when the osmotic properties of a solution are of interest (p. 49). 

Aluminium hydroxide acts primarily as a base, but it also ionises weakly as an acid pK = 12.2). The osmotic properties of sodium aluminate solutions are identical with those of NaOH both must have the same number of ions. Dissociations such as... 

Does Perry s Chemical Engineers Handbook contain information on densities of alcohol-water mixtures osmotic pressure of sodium chloride solutions corrosion properties of metals ... 

Bratko, D., and Vlachy, V. An application of the modified Poisson-Boltzmann equation in studies of osmotic properties of micellar solutions. Colloid and Polymer Science, 1985, 263, No. 5, p. 417—419. 

Classical cell physiology takes into account the effects of both ionic and nonionic solutes (for instance, in calculations of osmotic properties). Only fairly recently, however, has it become clear that physico-chemical parameters based on bulk measurements fail to account for many of the properties of large surface-to-volume-ratio systems. The explanation for these differences, which can be pronounced, must be sought in the long-range effects of interfaces on the structure and properties of water and aqueous solutions. 

Let us see how well we can use the rules to deduce the unknown osmotic properties of a cell. Figure la summarizes the changes in cell volume when cells were placed in three different experimental solutions. For the upper curve, cells were suspended in 0.3 osmolar sodium chloride. These cells are functionally impermeable to sodium chloride. The middle curve is the response of the cells when they were placed in 0.6 osmolar solution. The medium contained both sodium chloride, the impermeant solute, and a permeant nonelectrolyte. The lower curve was the response of the cells to 0.6 osmolar sodium chloride. 

The stability of the membranes obtained against various solvents was investigated by Immersing the membranes in the solvent concerned at 40°C for about three weeks. After that their mechanical and osmotic properties were tested again and compared with their properties before the treatment. The results of the experiments are shown in table I. The stability of the membranes subjected to cross-linking by an organic reagent is very satisfactory. Additional treatment with Cr(III) solutions... 

A Katchalsky, Z Alexandrawitcz. On the additivity of osmotic properties of polyelectrolyte solutions. J Polym Sci Al 2093-2099, 1963. 

Figure 5.8 CMC determination from a plot of a solution physical property such as surface tension, conductivity, turbidity, osmotic pressure, molar conductivity etc. versus concentration of surfactant added, c (preferably, a property - Inc plot can be used).

The interactions of ions with water molecules and other ions affect the concentration-dependent (colligative) properties of solutions. Colligative properties include osmotic pressure, boiling point elevation, freezing point depression, and the chemical potential, or activity, of the water and the ions. The activity is the driving force of reactions. Colligative properties and activities of solutions vary nonlinearly with concentration in the real world of nonideal solutions. 

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