Electrochemical series of the elements

Corrosion of iron is explained by the position of iron in the electrochemical series of the elements (Fe/Fe2+ —0.44 V). In steel, local anode and cathode areas are found due to the presence of phases containing, for example, carbon, carbides, and oxides. These latent local cells are activated by moisture, oxygen, and current-carrying electrolytes and the following reactions occur between the anode areas consisting of iron, and the cathode areas containing carbides or oxides. 

The reducing powers of metals parallel their relative electrode potentials, i.e. potentials developed when the metal is in contact with a normal solution of its salts. The potential of hydrogen being equal to 0, the potentials or electrochemical series of some elements are as shown in Table 4. 

What place do the chromium subgroup elements occupy in the electrochemical series of the metals How do they react with acids and with alkalies Write the equations of the relevant reactions. 

According to the electromotive series of the elements there are innumerable pairs which will yield electrochemical energy accumulators. For instance, take a metal and a metallic oxide and immerse them in a liquid electrolyte. These are the main parts of a cell as Figure 15.1 demonstrates. 

In the electrochemical series of elements, copper is near the noble end and will not normally displace hydrogen, even from acid solutions. Indeed, if hydrogen is bubbled through a solution of copper salts, copper is slowly deposited (more rapidly if the process is carried out under pressure). (See Section 1.2 for thermodynamic considerations.)... 

The ease with which an atom gains or loses electrons is termed the electronegativity of the element. Tabulation of the elements in order of ease by which they lose electrons is called the electrochemical series and is shown in Table 6.10. Chapter 4 explains the importance of this to the formation and control of corrosion, and Chapter 6 discusses the relevance to predicting reactivity of metals towards water and their potential to become pyrophoric. 

The electrochemical series corresponds only to the standard condition, i.e., for unit activity of the ions, since a change to another ionic concentration can alter the order of the electrode potentials of the elements very markedly. The case of nickel plating mentioned earlier may be taken as typically illustrative of the many practical examples of the effects and the consequences of nonstandard conditions. It must also be mentioned in the context of the examples of displacement reactions provided earlier that the concentrations and the electrode potentials frequently vary during a displacement reaction. 

K. K. Electrochemical Reactions in Non-aqueous Systems, Marcel Deldcer, New York, 1970, Chapter 14 (b) Meites, L., Zuman, P. (Eds) CRC Elandbook Series in Inorganic Electrochemistry, Vols I—VIII, CRC Press, Boca Raton, FL, 1980-1988 (c) Bard, A. J. (Ed.) Encyclopedia of Electrochemistry of the Elements, Vols I-XIV (Inorganic Section), Marcel Deldcer, New York, 1973-1980 (d) Reports from IU-PAC Commission on Electroanalytical Chemistry, Pure Appl. Chem.. 1977, 49, 217, 877 1983, 55, 1373. 

Write the electron configurations and the sizes of the atoms of the copper subgroup elements. What oxidation states do these elements exhibit in their compounds Give examples. What position do they occupy in the electrochemical series Write the equations of the reactions of copper, silver, and gold with acids. Give a comparative general characteristic of the physical and chemical properties of the elements of Group one. 

The considered electrochemical model has brought us to certain conclusions on the mechanism of polymer polarization in the M1-P-M2 systems. It is evident that definite electrode potentials are established on metals faces in contact with the polymer material. These potential values are affected by the work function of the electrons and metal afEnity to the corresponding structural elements of the polymer lining. These potentials are noncoincident with a standard electrochemical series of metals. This is natural, since the properties of polymer materials as electrolytes are not identical to those of salt solutions of the corresponding metals, for which the standard electrode potentials of metals are determined. The studied metals in pairs separated by the PVB lining are arranged in the following series ... 

The corrosion behavior of metals cannot be predicted from the position of their standard potentials in the electrochemical series because the potential of an electrode changes with the current density. If an electrode in which only one electrode process takes place is termed a working electrode and the resultant potential, a working potential, then the differences between working potential and the Nernst equilibrium potential is called an overpotential, that is caused by reaction restraints. In general, polarization is defined as the shift in potential of working electrodes within a corrosion element. In such an element, at least two electrode reactions occur whose overpotentials are superimposed, resulting in the polarization effect. 

In so far that the electrochemical series expresses the relative willingness of different elements to form cations or anions, it is not unreasonable to suppose that the same series will express the relative willingness of different elements to adopt an ionic structure in their compounds as against a covalent one. Thus,... 

The electrochemical series published in the literature must be differentiated as either the standard electrochemical series or the different practical electrochemical series, since the latter apply only to a certain given medium. The standard electrochemical series lists only the potentials of the pure elements in the list measured under standard conditions in a solution of their own salts against the normal hydrogen electrode. 

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