SOME THEORETICAL ASPECTS OF ELECTRON-TRANSFER PROCESSES IN AQUEOUS SOLUTION

1959 ◽  
Vol 37 (1) ◽  
pp. 138-147 ◽  
Author(s):  
Keith J. Laidler
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Free Energy ◽  
Energy Of Activation ◽  
Theoretical Treatment ◽  
Free Energy Of Activation ◽  
Diffusion Controlled ◽  
Entropy Of Activation ◽  
Pass Through ◽  
Electron Transfer Processes

A theoretical treatment has been developed for the rates of electron-transfer reactions in aqueous solution, with particular reference to the ferric–ferrous system. The reactions are considered to be diffusion-controlled processes, the approach of the ions being hindered by the electrostatic repulsion between them. Calculations have been made of the free energy of the diffusion process and for the repulsion, account being taken of the variation in dielectric constant with the electric field. The form of the potential-energy barrier between the ions is calculated for various separations, and the transmission coefficient calculated using the quantum-mechanical expression corresponding to a rectangular barrier. The total free energy of activation for the reaction, which is the sum of the contributions due to diffusion, repulsion, and tunnelling, is found to pass through a minimum at a separation of about 4 Å. The calculated free energy of activation for the reaction is 15.4 kcal, in good agreement with the experimental value of 16.8 kcal. The energy and entropy of activation for the reaction are also briefly discussed.

Densities and kinematic viscosities of tetra-n-butylammonium iodide–nickel(II) chloride melts

1979 ◽  
Vol 57 (2) ◽  
pp. 147-150
Author(s):  
Nurul Islam ◽  
Abdul Maroof ◽  
Ismail Kochi
Keyword(s):  
Free Energy ◽  
Viscous Flow ◽  
Kinematic Viscosity ◽  
Composition Dependence ◽  
Energy Of Activation ◽  
Slight Tendency ◽  
Free Energy Of Activation ◽  
Chloride Melts ◽  
Entropy Of Activation ◽  
Viscous Behaviour

Densities and kinematic viscosities of molten mixtures of nickel(II) chloride in tetra-n-butylammonium iodide have been measured as functions of temperature and composition. The data on the kinematic viscosity have been analyzed using both Arrhenius and non-Arrhenius type equations. The heat of activation, the entropy of activation, and the free energy of activation for viscous flow have been computed. At higher concentrations a slight tendency towards non-Arrhenius viscous behaviour is observed. The free energy of activation helps in describing the overall composition dependence of kinematic viscosity.

Role of solvation and desolvation in polymer ‘catalysis’. I. The influence of high pressures on the spontaneous and Ag+-induced aquations of Co(NH 3 )5Br 2+ catalysed by macro-ions

1980 ◽  
Vol 370 (1743) ◽  
pp. 485-500 ◽  
Keyword(s):  
Free Energy ◽  
High Pressures ◽  
Energy Of Activation ◽  
Elevated Pressures ◽  
Free Energy Of Activation ◽  
Entropy Of Activation ◽  
Activated Complex

The spontaneous and Ag+-induced aquation reactions of Co(NH 3 ) 5 Br 2 + were examined in the presence of polyelectrolytes and at high pressures. The aquation reactions were enhanced by addition of anionic polyelectrolytes, i.e. sodium polyethylenesulphonate and sodium polystyrenesulphonate. The polyelectrolyte-accelerated reactions were retarded at elevated pressures. The volumes of activation, ΔT≠, were negative in the absence of the macro-ions and positive in their presence for both aquations. The results indicate that the activated complex is dehydrated by the macro-ions to a much larger extent than the reactants. Correspondingly, the entropy of activation was increased by addition of the macro-ions, causing a decrease in the free energy of activation. The dehydration of the activated complex is thus considered to be one of the important factors of polyelectrolyte ‘catalysis’. The implications of these findings are discussed.

Viscosity of Dimethyl Sulfoxide + 1,4 Dimethylbenzene System

2008 ◽  
Vol 59 (1) ◽  
pp. 45-48
Author(s):  
Oana Ciocirlan ◽  
Olga Iulian
Keyword(s):  
Free Energy ◽  
Dimethyl Sulfoxide ◽  
Atmospheric Pressure ◽  
Entire Range ◽  
Polynomial Equation ◽  
Energy Of Activation ◽  
Excess Gibbs Free Energy ◽  
Experimental Measurements ◽  
Gibbs Energy Of Activation ◽  
Free Energy Of Activation

This paper reports the viscosities measurements for the binary system dimethyl sulfoxide + 1,4-dimethylbenzene over the entire range of mole fraction at 298.15, 303.15, 313.15 and 323.15 K and atmospheric pressure. The experimental viscosities were correlated with the equations of Grunberg-Nissan, Katti-Chaudhri, Hind, Soliman and McAllister; the adjustable binary parameters have been obtained. The excess Gibbs energy of activation of viscous flow (G*E) has been calculated from the experimental measurements and the results were fitted to Redlich-Kister polynomial equation. The obtained negative excess Gibbs free energy of activation and negative Grunberg-Nissan interaction parameter are discussed in structural and interactional terms.

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