Properties apparent molar

A method for determining partial molar properties, most often applied to electrolyte solutions, involves using the apparent molar property [Pg.222]

In Chapter 5, with equation (5.43). we defined the apparent molar property Z as... 

When a solute particle is introduced into a liquid, it interacts with the solvent particles in its environment. The totality of these interactions is called the solvation of the solute in the particular solvent. When the solvent happens to be water, the term used is hydration. The solvation process has certain consequences pertaining to the energy, the volume, the fluidity, the electrical conductivity, and the spectroscopic properties of the solute-solvent system. The apparent molar properties of the solute ascribe to the solute itself the entire change in the properties of the system that occur when 1 mol of solute is added to an infinite amount of solution of specified composition. The solvent is treated in the calculation of the apparent molar quantities of the solute as if it had the properties of the pure solvent, present at its nominal amount in the solution. The magnirndes of quantities, such as the apparent molar volume or heat content, do convey some information on the system. However, it must be realized that both the solute and the solvent are affected by the solvation process, and more useful information is gained when the changes occurring in both are taken into account. 

In forming a mixed micelle, solute 3 will shift the CMC of solute 2 to lower values, and this will be reflected In the apparent molar properties of solute 3 In the CMC region of solute 2. 

It can be shown by starting with the definition of the apparent molar property and differentiating that the apparent molar quantities are related by the same equations as the molar quantities. Thus if,... 

Figure 6.1 illustrates the concept of the apparent molar volume. AB is the portion of the total volume AC for n2 moles of solute that is attributed to the pure solvent. Then, the volume BC is apparently due to the solute. The slope of the line passing through point C and V is the apparent molar volume. The slope of the curve of the total volume at point C is the partial molar volume of component 2. Indeed, the slope of the total volume curve at any point is the partial molar volume of component 2 at that concentration. It is obvious that partial molar properties and apparent molar properties are both functions of concentration. 

In order to indicate the fact that the value of G as given by equation (42.1) applies to the constituent 2, i.e., the solute, a subscript 2 is sometimes included. However, this is usually omitted, for in the great majority of cases it is understood that the apparent molar property refers to the solute. It i.s seen from equation (42.1) that o is the apparent contribution of 1 mole of the component 2 to the property G of the mixture. If the particular property were strictly additive for the two components, e.g., volume and heat content for ideal gas and liquid solutions, the value of 4>q would be equal to the actual molar contribution, and hence also to the partial molar value. For nonideal systems, however, the quantities are all different. 

Kon kova TS, Matyushin YuN, Miroshnichenko EA, Vorob ev AB (2009) Thermochemical properties of dinitramidic acid salts. Russ Chem Bull Inti Ed 58 2020-2027 Kumar A (2001a) Aqueous guanidinium salts Part ll. Isopiestic osmotic coefficients of guanidinium sulphate and viscosity and surface tension of guanidinium chloride, bromide, acetate, perchlorate and sulphate solutions at 298.15 K. Eluid Phase Equil 180 195-204 Kumar A (2001b) Aqueous guanidinium salts part I. Densities, ultrasonic velocities, and apparent molar properties. J Solution Chem 30 281-290... 

The first thing we come across when looking at real data is that quite often the data are reported as apparent molar volumes, enthalpies, entropies or heat capacities. If we call component 1 the solvent (usually water in our cases), component 2 the solute (say, NaCl), Z and Z the total and molar forms of any of these properties, then apparent molar properties are defined as... 

Here a brief survey will be made about the recent developments on the subject regarding the hydration functions and the apparent molar properties (j = v, Cp, E, k) of non-charged solutes in aqueous solution. In order we will examine the progresses achieved ... 

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