Kinetics and Mechanism of Zn(II) Ion Electroreduction in the Presence of Vetranal

2008 ◽  
Vol 73 (5) ◽  
pp. 616-626 ◽  
Author(s):  
Jolanta Nieszporek ◽  
Dorota Gugała-Fekner ◽  
Dorota Sieńko ◽  
Jadwiga Saba ◽  
Krzysztof Nieszporek
Keyword(s):  
Electron Transfer ◽  
Mercury Electrode ◽  
Surface Excess ◽  
Forward Reaction ◽  
True Rate ◽  
Half Wave ◽  
Reversible Potential ◽  
Dropping Mercury Electrode ◽  
Dc Polarography ◽  
Bridging Model

The two-step reduction of Zn(II) ions at a dropping mercury electrode in 1 M NaClO4 with addition of vetranal was examined using dc polarography, cyclic voltammetry and impedance measurements. Small changes of reversible potential of half-wave, Er1/2, values indicate that the Zn(II)-vetranal complexes formed in the solution are very unstable. A stepwise character of electron transfer in the Zn(II) ion reduction was established. The catalytic activity of vetranal is stronger in the first step of electron transfer than in the second one. The linear dependence of the true rate constant for the forward reaction, ktf, of Zn(II) electroreduction versus relative surface excess, Γ′, of vetranal at a given potential in the reaction plane, Φr, was interpreted in terms of a "bridging model".

Reduction of indium(III) at dropping mercury electrode in the presence of pyridine in aqueous and ethanol–water media

2010 ◽  
Vol 75 (6) ◽  
pp. 653-663 ◽  
Author(s):  
Vinita Sharma ◽  
Krishna D. Gupta
Keyword(s):  
Mercury Electrode ◽  
Complexation Reaction ◽  
Complex Species ◽  
Diffusion Controlled ◽  
Straight Line ◽  
Half Wave ◽  
Dropping Mercury Electrode ◽  
Water Media ◽  
Single Complex ◽  
The Stability

The reduction of indium(III) at dropping mercury electrode in aqueous as well as in 25% ethanol–water media in the presence of pyridine has been studied at a constant ionic strength (0.1 M KNO3) and at 30 and 40 °C. The reduction is diffusion-controlled but the electrode process is quasi-reversible in both media. The reversible half-wave potential values,E1/2r, have been obtained by Gelling’s method. The plot ofE1/2r versus pyridine concentration is a straight line and the number of ligands,j, was determined from the slope. This shows the formation of a single complex. The stability constant has been determined by Lingane’s method. In(III) forms one complex species with composition 1:1, [In(py)]3+. The values of thermodynamic parameters ΔG, ΔHand ΔSof the complexation reaction have also been determined at 30 °C.

The Influence of N,N'-Dialkylthioureas on the Two-Step Electroreduction of Zn(II) Ions

1998 ◽  
Vol 63 (6) ◽  
pp. 749-760 ◽  
Author(s):  
Grażyna Dalmata
Keyword(s):  
Electron Transfer ◽  
Double Layer ◽  
Rate Constant ◽  
Electrode Surface ◽  
Mercury Electrode ◽  
Impedance Method ◽  
Dropping Mercury Electrode ◽  
Wide Potential ◽  
Orientation Of Molecules

A two-step reduction of Zn(II) ions at the dropping mercury electrode in 1 M NaClO4/0.001 M HClO4 in the presence of N,N'-dialkylthioureas was examined in wide potential and frequency ranges, using the impedance method. The rate constant of the first electron transfer increases with increasing concentration of N,N'-dialkylthioureas, whereas that of the second electron transfer depends largely on the double layer effects, particularly, on the orientation of molecules on the electrode surface.

Faradaic Impedance Study of Mn(II) Reduction Mechanism in NaClO4 and NaCl Solutions on Mercury Electrode

2002 ◽  
Vol 67 (11) ◽  
pp. 1589-1595
Author(s):  
Barbara Marczewska ◽  
Andrzej Persona ◽  
Marek Przegaliński
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Electrochemical Reaction ◽  
Mercury Electrode ◽  
Reduction Mechanism ◽  
True Rate ◽  
Faradaic Impedance ◽  
Impedance Measurements ◽  
Order Of Magnitude ◽  
Adsorptive Properties

The electrochemical reaction of the Mn(II)/Mn(Hg) system on mercury electrode was studied in 1 M NaClO4 and 1 M NaCl as supporting electrolytes of different complexing and adsorptive properties. The impedance measurements confirmed the two-stage electroreduction of the Mn(II) in investigated solutions. Both the apparent and the true rate constants of the second electron transfer in both supporting electrolytes are lower by one order of magnitude than the rate constant of the first electron transfer. Similar values of corrected rate constants in both electrolytes suggest the similarity in mechanism of the Mn(II) electroreduction.

scholarly journals Reduction of Cd(II) Ions in the Presence of Tetraethylammonium Cations. Adsorption Effect on the Electrode Process

Electrochem ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 415-426
Author(s):  
Juan Torrent-Burgués
Keyword(s):  
Mercury Electrode ◽  
Reduction Process ◽  
Inhibitory Effect ◽  
Electrode Process ◽  
Adsorption Effect ◽  
A Value ◽  
Half Wave ◽  
Dropping Mercury Electrode ◽  
Electrode Coverage ◽  
Isotherm Equations

The effect of the adsorption of tetraethylammonium (TEA) cations, which present both ionic and organic characteristics, on the reduction of Cd(II) ions have been studied from dc and ac measurements at the dropping mercury electrode. The resistance to the charge transfer (Rct) and Warburg coefficient (σ) parameters have been determined through impedance measurements. Thus, the global velocity constant has been obtained. The reduction process of Cd(II) in perchloric media is reversible and is affected by the adsorption of TEA cations, especially at high TEA concentrations. Values of E1/2, half wave potential, and DO, diffusion coefficient, obtained from both dc and ac measurements agree. The velocity constants show a decrease as TEA concentration increases, with values ranging from 0.6 to 0.01 cm·s−1. The inhibitory effect of TEA adsorption on the electrode process and the relationship between electrode coverage, θ, and velocity constants, K, using several isotherm equations, have been discussed. The best fit was obtained with the equation K = 0K(1 − θ)a with an a value close to three, indicating a blocking effect and electrostatic repulsion due to TEA.

Cathodic action of lead malate complexes at the dropping mercury electrode

1973 ◽  
Vol 26 (5) ◽  
pp. 971 ◽  
Author(s):  
SC Khurana ◽  
CM Gupta
Keyword(s):  
Stability Constants ◽  
Mercury Electrode ◽  
Reduction Reaction ◽  
Ligand Concentration ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave ◽  
Dropping Mercury Electrode ◽  
The Stability

The electrode reduction reaction of lead malate, involving deprotonated malate ion and a proton, between pK1 and pK2 values of the acid has been investigated. At pH < pK1 protonated ion participates and a proton is involved. The effect of ligand concentration on the half-wave potential of Pb2+ has been investigated and the stability constants of species so formed computed.

Polarographic and Voltammetric Determination of Chlorobenzene, Benzyl Chloride and Melphalan

1992 ◽  
Vol 57 (3) ◽  
pp. 450-456 ◽  
Author(s):  
Jiří Barek ◽  
Jaroslav Matějka ◽  
Jiří Zima
Keyword(s):  
Benzyl Chloride ◽  
Mercury Electrode ◽  
Differential Pulse ◽  
Differential Pulse Polarography ◽  
Water Medium ◽  
Pulse Polarography ◽  
Half Wave ◽  
Dropping Mercury Electrode ◽  
Pulse Voltammetry

Conditions were found for the determination of chlorobenzene and benzyl chloride in dimethylformamide and of Melphalan in ethanol-water medium (4 : 1) using tast polarography at a classical dropping mercury electrode in the concentration range 1 . 10-3 - 2 . 10-5 mol l-1. Differential pulse polarography permits the range for the determination of benzyl chloride to be extended to 1 . 10-5 - 2 . 10-6 mol l-1. The use of fast scan differential pulse voltammetry and linear scan voltammetry at a hanging mercury drop electrode did not lead to an increase in the sensitivity of the determination because of the very negative half-wave potential values and high irreversibility of the processes involved.

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