Discreteness-of-charge effects in electrode kinetics. I. The electroreduction of tetrathionate anion in the presence of specifically adsorbed iodide anions

1982 ◽  
Vol 60 (15) ◽  
pp. 2038-2045 ◽  
Author(s):  
W. Ronald Fawcett ◽  
Kveta Markušová
Keyword(s):  
Ionic Strength ◽  
Electrode Potential ◽  
Ion Concentration ◽  
Electrode Kinetics ◽  
Charge Effect ◽  
Charge Effects ◽  
Potential Analysis ◽  
Rate Of Reaction ◽  
Kinetics Of ◽  
Outer Helmholtz Plane

The kinetics of electroreduction of tetrathionate anion have been studied at a Hg electrode in aqueous solutions of Nal + NaF and KI + KF with an ionic strength of 0.25 M. The rate of reaction was observed to decrease as the iodide ion concentration was increased, and when the cation was changed from K+ to Na+ at constant electrode potential. Analysis of the double layer effects on the basis of the Frumkin model results in an overestimation of the repulsive effect of the adsorbed iodide anions. This result is interpreted on the basis of the discreteness-of-charge effect and the possible non-coincidence of the reaction plane and outer Helmholtz plane.

Discreteness-of-charge effects in electrode kinetics. III. The electroreduction of aquopentamminochromium(III) cation in the presence of specifically adsorbed iodide anions

1984 ◽  
Vol 62 (8) ◽  
pp. 1497-1501 ◽  
Author(s):  
W. Ronald Fawcett ◽  
Kveta Markušová
Keyword(s):  
Ionic Strength ◽  
Electrode Kinetics ◽  
Reaction Site ◽  
Charge Effects ◽  
Iodide Concentration ◽  
Rate Acceleration ◽  
Rate Of Reaction ◽  
Layer Effect ◽  
Kinetics Of ◽  
Outer Helmholtz Plane

The kinetics of electroreduction of the aquopentamminochromium(III) cation have been studied at a Hg electrode in acidified aqueous solutions of NaI+ NaClO4 with an ionic strength of 0.25 M. The rate of reaction increased with increase in iodide concentration due to the accelerating effect of this anion when it is adsorbed on the electrode. Analysis of the double layer effect indicates that the rate acceleration is greater than that predicted by the Frumkin theory chiefly because the reaction site is closer to the electrode than to the outer Helmholtz plane.

Discreteness-of-charge effects in electrode kinetics. II. The electroreduction of hexamminocobalt(III) cation in the presence of specifically adsorbed nitrate anions

1983 ◽  
Vol 61 (12) ◽  
pp. 2821-2826 ◽  
Author(s):  
W. Ronald Fawcett ◽  
Kveta Markušová
Keyword(s):  
Ion Pairs ◽  
Electrode Reaction ◽  
Ion Concentration ◽  
Charge Effects ◽  
Interfacial Kinetics ◽  
Rate Of Reaction ◽  
Layer Effect ◽  
Kinetics Of ◽  
Nitrate Anions ◽  
Cation Nature

The kinetics of electroreduction of the hexamminocobalt(III) cation have been studied at a Hg electrode in aqueous solutions of NaNO3 + NaF and KNO3 + KF with an ionic strength of 0.2 M. The rate of reaction was observed to increase with increasing nitrate ion concentration but was independent of the cation nature. Analysis of the double layer effect for this system indicates that ion pairs formed between the reacting cation and anions of the base electrolyte also participate in the electrode reaction, and that attractive interactions between the reactant and adsorbed anions have a significant influence on the interfacial kinetics.

Analysis of the Electrode Kinetics of Ni(II) Reduction in Thiocyanate Media on the Dropping Mercury Electrode

2000 ◽  
Vol 65 (3) ◽  
pp. 326-342
Author(s):  
María S. Crespo-Pinilla ◽  
Fernando Mata-Pérez ◽  
Rosa M. Villamañán
Keyword(s):  
Ionic Strength ◽  
Compensation Effect ◽  
Supporting Electrolyte ◽  
Mercury Electrode ◽  
Electrode Kinetics ◽  
Surface Process ◽  
Experimental Conditions ◽  
Dropping Mercury Electrode ◽  
Kinetics Of

A study of two prewaves of the Ni(II)-SCN- system was carried out under the experimental conditions when the influence of electroreduction of SCN- is negligible. Kinetics of Ni(II) reduction in thiocyanate media on the dropping mercury electrode was studied by DC Tast Polarography (DCTP) via determination of Koutecký's parameter χ; the influence of different variables was analyzed. The study of prewaves was performed using various polarographic techniques. Values of χ depend on the SCN- concentration, pH, ionic strength (Ψ-effect) and on the nature of the supporting electrolyte. The number of electrons n, the transfer coefficient α, the stoichiometric number ν, ∆H≠, and ∆S≠ were determined (compensation effect). The first prewave has character of a reaction in the solution, the second prewave is a surface process. Main features of both mechanisms are common: catalytic nature, one-electron step discharge and the rate-determining process between species of opposite charges.

Influence of Aqueous Mixtures of Amides on the Kinetics of Electro Reduction of Ni(II) and Co(II) at d. m. e.

1975 ◽  
Vol 30 (11-12) ◽  
pp. 859-861 ◽  
Author(s):  
S. K. Jha ◽  
S. Jha ◽  
S. N. and
Keyword(s):  
Rate Constants ◽  
Electrode Potential ◽  
Gradual Decrease ◽  
Electrode Kinetics ◽  
Aqueous Mixtures ◽  
Aqueous Mixture ◽  
Kinetics Of ◽  
Remarkable Agreement ◽  
Amide Content

Electroreduction of Ni(II) and Co(II) has been carried out in aqueous mixtures of formamide, acetamide and urea. Electrode kinetics in terms of theories of irreversible waves have been studied. After calculating the rate constants by DELAHAY1 and Kou-TECKY2 treatments separately their variation with electrode potential has been used to calculate the product ‘ana’. The rate constants and ‘ana’ calculated from two different approaches show remarkable agreement. `ana’ records a gradual decrease with increasing amide content of the aqueous mixture.

Mechanistic Information from the Effect of Pressure on the Kinetics of Hydrolysis of Iodopentaaquochromium(III) Ion

1975 ◽  
Vol 53 (24) ◽  
pp. 3697-3701 ◽  
Author(s):  
Milton Cornelius Weekes ◽  
Thomas Wilson Swaddle
Keyword(s):  
Ionic Strength ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Kinetics Of Hydrolysis ◽  
Rate Of Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Aqueous Hclo ◽  
Conjugate Base

The rate of hydrolysis of iodopentaaquochromium(III) ion has been measured as a function of pressure (0.1 to 250 MPa) and hydrogen ion concentration (0.1 to 1.0 mol kg−1) at 298.2 K and ionic strength 1.0 mol kg−1 (aqueous HClO4–LiClO4). The volumes of activation for the acid independent and inversely acid dependent hydrolysis pathways are −5.4 ± 0.5 and −1.6 ± 0.3 cm3 mol−1 respectively, and are not detectably pressure-dependent. Consideration of these values, together with the molar volume change of −3.3 ± 0.3 cm3 mol−1 determined dilatometrically for the completed hydrolysis reaction, indicates that the mechanisms of the two pathways are associative interchange (Ia) and dissociative conjugate base (Dcb) respectively.

THE REACTION BETWEEN CYANATE AND HYPOCHLORITE

1956 ◽  
Vol 34 (4) ◽  
pp. 489-501 ◽  
Author(s):  
M. W. Lister
Keyword(s):  
Activation Energy ◽  
Ionic Strength ◽  
Rate Constant ◽  
Hypochlorous Acid ◽  
Effect Of Temperature ◽  
Slow Step ◽  
True Activation Energy ◽  
Rate Of Reaction ◽  
Different Temperatures ◽  
Kinetics Of

The reaction between sodium hypochlorite and potassium cyanate in the presence of sodium hydroxide has been examined. The main products are chloride, and carbonate ions and nitrogen; but, especially if much hypochlorite is present, some nitrate is formed as well. The rate of reaction is proportional to the cyanate and hypochlorite concentrations, but inversely proportional to the hydroxide concentration: the rate constant is 5.45 × 10−4 min.−1 at 65 °C, at an ionic strength of 2.2. The rate constant increases somewhat as the ionic strength rises from 1.7 to 3.5. The effect of temperature makes the apparent activation energy 25 kcal./gm-molecule. The kinetics of the reaction suggest that the slow step is really a reaction of hypochlorous acid and cyanate ions, and possible intermediate products of this reaction are suggested. Allowing for the different extent of hydrolysis of hypochlorite at different temperatures, the true activation energy is found to be 15 kcal./gm-mol., which is consistent with the observed rate of reaction.

scholarly journals Acid Hydrolysis of Bis(2,2'; 6',2''–Terpyridyl) Iron(II) Complex in the Water Pools of CTAB/Hexane/Chloroform Reverse Micelles-A Kinetic Study in Confined Medium

2020 ◽  
Vol 15 (3) ◽  
pp. 853-860
Author(s):  
K. V. Nagalakshmi ◽  
P. Shyamala
Keyword(s):  
Ionic Strength ◽  
Acid Hydrolysis ◽  
Reverse Micelles ◽  
Order Rate Constant ◽  
Micellar Medium ◽  
First Order ◽  
First Order Kinetics ◽  
Rate Of Reaction ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of acid hydrolysis of bis(2,2';6',2''–terpyridyl) iron(II) complex has been studied in CTAB/Hexane/Chloroform reverse micelles. The reaction obeys first order kinetics with respect to each of the reactants at all values of W, {W= [H2O]/[CTAB]}. In the reverse micellar medium, the reaction is much slower compared to aqueous medium due to low micropolarity of the water pools which does not facilitate a reaction between reactants of same charge. The effect of variation of W {W=[H2O]/[CTAB]} at constant [CTAB] and variation of [CTAB] at fixed W has been studied. The second order rate constant (k2) of the reaction increases as the value of W increases up to W = 8.88 and remains constant thereafter and it is independent of concentration of [CTAB] at constant W. The variation of rate of reaction with W has been explained by considering variation of micropolarity and ionic strength of water pools of reverse micelles with W. Copyright © 2020 BCREC Group. All rights reserved 

The effects of counter ion nature on the adsorption of nitrate ion at the mercury/solution interface

1977 ◽  
Vol 55 (22) ◽  
pp. 3871-3881 ◽  
Author(s):  
W. Ronald Fawcett ◽  
James B. Sellan
Keyword(s):  
Ionic Strength ◽  
Ion Concentration ◽  
Surface Excess ◽  
Charge Effects ◽  
Nitrate Ion ◽  
Anion Adsorption ◽  
Solution Interface ◽  
Ionic Adsorption ◽  
Counter Ion ◽  
Capacity Data

The adsorption of nitrate ion at mercury has been studied from two systems at constant ionic strength, namely, xM NaNO3 + (0.2 − x) M NaF and x M KNO3 + (0.2 − x) M KF. The surface excess due to adsorbed nitrate ions was determined from differential capacity data using a modified version of the Hurwitz–Parsons analysis which takes into consideration variation in ionic activity coefficients with solution composition. The amount of adsorbed nitrate ion at a given electrode charge density and bulk nitrate ion concentration is shown to depend markedly on both ionic strength and the nature of the counter ion at the outer Helmholtz plane; when the charge in the diffuse layer is positive, an increase in ionic strength results in more anion adsorption and vice versa. A change in the cation from Na+ to K+ also results in increased anion adsorption. The effects observed are discussed in terms of the Stern–Grahame–Levine model for ionic adsorption which is based on an electrostatic description of the charged interface with consideration of discreteness-of-charge effects.

The mean spherical approximation and medium effects in the kinetics of solution reactions involving ions

1997 ◽  
Vol 75 (11) ◽  
pp. 1649-1655 ◽  
Author(s):  
W. Ronald Fawcett ◽  
Alex C. Tikanen ◽  
Douglas J. Henderson
Keyword(s):  
Ionic Strength ◽  
Infinite Dilution ◽  
Electrolyte Concentration ◽  
Spherical Approximation ◽  
Mean Spherical Approximation ◽  
Medium Effects ◽  
Kinetics Studies ◽  
Rate Of Reaction ◽  
The Mean ◽  
Kinetics Of

The mean spherical approximation has been applied to describe medium effects in the kinetics of reactions between ions in water. When the ionic strength of the medium is altered by the addition of an inert electrolyte, the rate of reaction can be accurately predicted with the inert electrolyte concentration up to 1 M. The theoretical rate constant at the limit of infinite dilution kr0, has been estimated for five earlier kinetics studies for which data are available in the literature. Keywords: kinetic medium effects, mean spherical approximation, activity coefficients.

scholarly journals The mechanism of the iodination of aminochromes

1967 ◽  
Vol 45 (15) ◽  
pp. 1721-1725 ◽  
Author(s):  
G. L. Mattok ◽  
D. L. Wilson
Keyword(s):  
Potassium Iodide ◽  
Molecular Iodine ◽  
Reactive Species ◽  
Base Catalysis ◽  
Ion Concentration ◽  
Zwitterionic Form ◽  
General Base ◽  
Rate Of Reaction ◽  
Reaction Proceeds ◽  
Kinetics Of

The kinetics of the iodination of several aminochromes by iodine in aqueous potassium iodide, to form the 7-iodo derivatives, have been studied. The rate of iodination is directly dependent on the concentrations of the aminochrome and iodine and varies inversely with the first power of the iodide ion concentration. The rate of reaction is independent of pH, but the reaction is subject to general base catalysis. A mechanism for the iodination of aminochromes is proposed. The reactive species are molecular iodine and the zwitterionic form of adrenochrome, and the reaction proceeds via a quinonoid intermediate. The rate-controlling process is the removal of the C-7 proton.

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