Molar conductivity temperature dependence

Due to the fact that K2TaF7 - KF is considered to be part of the TaF5 - KF binary system, while the K2TaF7 - KCI system is a component of the interconnected ternary system K+, Ta5+//F", Cl", the single-molecule conductivity and activation energy of the systems was calculated based on density and specific conductivity data [322, 324]. Molar conductivity (p) depends on the absolute temperature (T), according to the following exponential equation ... 

Table 2.5.1 lists the molar conductivities of some ions in dilute solution. There is a strong temperature dependence and, as with mass diffusivity, the conductivity increases exponentially with absolute temperature. The molar conductivity also depends on the electrolyte concentration falling off with increasing concentration, the drop being more rapid for weak electrolytes than for strong ones (see, e.g., Castellan 1983). 

In conclusion, from a non-selective conductivity measurement, it is possible to find specific ion concentrations by recording the conductivity at different temperatures. The key to this is that every ion has its own specific limiting molar conductivity which depends uniquely on temperature. This method needs an assumed set of ions the electrolyte conductivity is a linear combination of the specific ionic conductivities of these ions. 

Fig- 23. Temperature dependence of the maximum equivalent conductivity Amax for PDADMAC with different molar masses and DADMAC (Data taken from [38])... 

Experiments on ILs have generally shown a highly non-Arrhenius behavior that is well described by the VFT equation. Xu et al. [149] report the temperature-dependent viscosity of a series of covalently stable ILs, and note that the VFT equation fits the temperature dependence of the fluidity quite well. A series of studies by Watanabe and co-workers [167-169] on a range of different ILs shows that the VFT provides a good fit to diffusion constants, molar conductivity and viscosity. 

The temperature dependence of molar conductivity, calculated from ionic conductivity determined from complex impedance measurements and molar concentrations, and the VFT fitting curves are shown Figure 5.8. The VFT equation for molar conductivity is... 

The [Fe(phen)3]3+ complex dissolved in water is known to behave as a hydrophobic ion, as demonstrated by the ion association with o- and m-benzenedisulfonate and 2,6- and 2,7-naphthalenedisulfonate ions, which was investigated by the conductivity method. Similar hydrophobic properties were also observed for trivalent [Co(phen)3]3+ and [Co(bpy)3]3+ complexes.2 In the present study, the temperature dependence of molar conductivities of [Fe(phen)3]2+, [Co(phen)3]3+, and [Co(bpy)3]3+ as well as the ion association with chloride and perchlorate ions were examined in order to elucidate the effect of the ionic charge on the hydrophobic interactions. 

Another way of examining the mechanism of proton transfer is by comparing its temperature dependence with that of other monoatomic cations. Plots of the molar conductance of three cations, namely, H, Li, and K, on a logarithmic scale are shown as a function of reciprocal temperature in the range 5-55°C in fig. 6.14. Excellent linear plots are found from which an energy barrier associated with the process may be calculated. Using a simple Arrhenius expression, the temperature dependence of X,- for a small temperature interval is given by... 

The heat conduction flux is given by — fc dT/dz aed for ideal vapors partial molar enthalpies (/f.) depend only on temperature. Substitution and integration result in an expression for the ratio of Ihe heat transfer coefficient with and without mass transfer ... 

The molar conductivity A of an electrolyte solution is defined as the conductivity divided by amount-of-substance concentration. The customary unit is S cm mol (i.e., cm moT ). The first part of this table gives the molar conductivity of the hydrohalogen adds at 25 °C as a function of the concentration in mol/L. The second part gives the temperature dependence of A for HCI and HBr. More extensive tables and mathematical representations may be found in the reference. 

Osmotic pressure (IT) - The excess pressure necessary to maintain osmotie equilibrium between a solution and the pure solvent separated by a membrane permeable only to the solvent. In an ideal dilute solution n = c RT, where Cb is the amount-of-substance concentration of the solute, is the molar gas constant, and T the temperature. [1,2] Ostwald dilution law - A relation forthe concentration dependence ofthe molar conductivity A of an electrolyte solution, viz.,... 

In this table, all units are based on the molar scale and was obtained from the temperature dependence of the overall formation constant Based on the differences in these quantities with the two supporting electrolytes, the ion-association constant for LiCl was estimated as 10 -, which is in good agreement with the value 10 obtained from conductivity data. In PC-H2O mixtures up to [H2O] = 3.57 molar, the various equilibrium constants are given by... 

Figure 6 shows the dependence on concentration and temperature of the molar conductivity of 1,2-dimethoxyethane solutions of LiBF4 from infinite dilution to saturation. The plots of A versus show a minimum at moderate concentrations and a maximum at high concentrations. Although the minimum is only weakly dependent on temperature, the maximum exhibits a strong displacement. The minimum is a general feature of bilateral triple-ion formation ... 

Figure 1. Molar conductivity A of KCl in KCl-H20-solutions in its dependence on density p and temperature (in C). Mole fraction of KCl 1.8 x 10 0.01 molar at normal conditions) [15]...

The conductance of an electrolyte solution is a property that determines the extent of movement of all ionic species in the solution upon the application of an electric field, resulting in the flow of the current through the solution. A complementary property is defined, the trans-ferance number, which expresses the relative extent to which only one kind of ion contributes to the charge transport. The conductance is the sum of the ionic conductances, whereas the transferance numbers depend on their ratio. Conductance yields unique information as to the nature of the structure of electrolytes, their equilibria and the ionic composition of liquids. Conductance depends on concentration and on external parameters, temperature and pressure. The concentration dependence of conductance indicates the ion-ion interactions such as the ion-pair formation and dissociation equilibria. On the other hand, the limiting values of the molar conductance (conductance/concentration) obtained by extrapolation for an infinitesimal dilution are functions only of the ion-solvent interactions. 

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