Electrochemical equivalents

In voltammetry a time-dependent potential is applied to an electrochemical cell, and the current flowing through the cell is measured as a function of that potential. A plot of current as a function of applied potential is called a voltammogram and is the electrochemical equivalent of a spectrum in spectroscopy, providing quantitative and qualitative information about the species involved in the oxidation or reduction reaction.The earliest voltammetric technique to be introduced was polarography, which was developed by Jaroslav Heyrovsky... 

Earlier we described a voltammogram as the electrochemical equivalent of a spectrum in spectroscopy. In this section we consider how quantitative and qualitative information may be extracted from a voltammogram. Quantitative information is obtained by relating current to the concentration of analyte in the bulk solution. Qualitative information is obtained from the voltammogram by extracting the standard-state potential for the redox reaction. For simplicity we only consider voltammograms similar to that shown in Figure 11.33a. 

Corrosion Rate by CBD Somewhat similarly to the Tafel extrapolation method, the corrosion rate is found by intersecting the extrapolation of the linear poi tion of the second cathodic curve with the equihbrium stable corrosion potential. The intersection corrosion current is converted to a corrosion rate (mils penetration per year [mpy], 0.001 in/y) by use of a conversion factor (based upon Faraday s law, the electrochemical equivalent of the metal, its valence and gram atomic weight). For 13 alloys, this conversion factor ranges from 0.42 for nickel to 0.67 for Hastelloy B or C. For a qmck determination, 0.5 is used for most Fe, Cr, Ni, Mo, and Co alloy studies. Generally, the accuracy of the corrosion rate calculation is dependent upon the degree of linearity of the second cathodic curve when it is less than... 

Crystal structure Interatomic distance Electrochemical equivalent (g/Ah) Density at 293 K (kg/m )... 

Electrochemical Equivalent number of moles of substance reacted electro-chemically by the passage of 1 Faraday of charge. 

The electrode potential of lithium is -3.01 V vs. NHE, which is the lowest value among all the metals. Lithium has the lowest density (0.54gcnrf3) and the lowest electrochemical equivalent (0.259 g Ah-1) of all solids. As a result of these... 

The electrochemical equivalent of iron (if only the first step is taken into account) is 960 Ah/kg and the open-circuit voltage of the nickel/iron cell is 1.4 V. 

The electrochemical equivalent of the lead is the lowest of all metallic anodes (260 Ah/kg) but in many applications the high open-circuit voltage of 2.1 V per cell compensates for this disadvantage. 

The electrochemical equivalent of 3860 Ah/kg is the highest among all metal anodes and the open-circuit voltage of 2.7-2.8 V (depending on electrolyte concentration) is rather high too. 

The zinc electrode is probably the most widely used metallic negative. The material is relatively cheap, has a good electrochemical equivalent (820 Ah/kg), and shows high open-circuit voltages (OCVs) in most systems (Table 1). 

The heat of reaction when one electrochemical equivalent of zinc displaces copper in sulphate solution is 2 592 cal. = — q... 

Current density Current efficiency Electrochemical equivalent... 

The volume of the metal produced depends on the current density, the electrolysis time, the cathode area, and the electrochemical equivalent. Yt is usually expressed as a function of the current density. The interrelationship among Yt, the specific area of the cathode, As (m2/m3), i.e., the area of the cathode per unitvolume of the reactor (cathode area/volume of the cell), the fractional current efficiency, T, and the current density, I, is given by ... 

Investigation of intermediates of an electrode reaction and rapid determination of the electrochemical equivalents may be achieved by means of thin-layer electrolytic cell only about 10 im thick, consisting of two platinum electrodes which are the opposing spindle faces of an ordinary micrometer. 

Magnesium is a reactive metal with relatively high electrochemical equivalent of 2.2 Ah/g and low specific gravity 1.74 g/cm3 its price is not high. This makes magnesium suitable for use as anode in metal-air cells. 

Reduction of phenyldiazonium chloride in acetonitrile containing a high concentration of an aromatic substrate, which can act as a free-radical trap, leads to phenylation of the substrate in 14 - 33% yields together with 50 - 50% of benzene formed by phenyl radical attack on the acetonitrile [132], Intramolecular capture of the phenyl radical, in an electrochemical equivalent of the Pschorr reaction, is much more successful and phenanthrene derivatives can be prepared in 90 - 96% yield [133],... 

Professor of physics at Cavendish Laboratory, Cambridge. He made elaborate investigations of the electrochemical equivalent of silver and of the combining volumes and compressibilities of gases. His observation that nitrogen prepared from the atmosphere is heavier than nitrogen prepared from ammonia led to the discovery of argon, the first noble gas. He also contributed to optics and acoustics. 

The advantage is that the electrode potential, E, can be varied continuously and that the intrinsic barrier is defined only by the acceptor. A drawback, however, is related to the effect of the electric double layer. If this effect is neglected, the electrochemical equivalents of equations (7) and (53) are equations (56) and (57). Now, E = E° when a = 0.5... 

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