Electrode reduction potentials

Electrode reduction potentials of mercury are given in Table 4. 

TABLE 4.2 Some Standard Electrode (Reduction) Potentials in Aqueous Solution at 25°C... 

Table 6.2 Selected Standard Electrode Reduction Potentials E d in Water (V vs. NHE) at 298.15 K, Assuming Unimolar Concentrations or Activities for Solutes and Unit Pressures or Fugacities for Gases (Ordered First by Potential, then Alphabetically) ...

Each electrode reaction, anode and cathode, or half-cell reaction has an associated energy level or electrical potential (volts) associated with it. Values of the standard equilibrium electrode reduction potentials E° at unit activity and 25°C may be obtained from the literature (de Bethune and Swendeman Loud, Encyclopedia of Electrochemistry, Van Nostrand Reinhold, 1964). The overall electrochemical cell equilibrium potential either can be obtained from AG values or is equal to the cathode half-cell potential minus the anode half-cell potential, as shown above. 

Of all possible reductions that might occur electrolytically at a cathode, the one for which the corresponding electrode potential is algebraically greatest is the most likely. Conversely, the most probable anodic oxidation is that for which the corresponding electrode (reduction) potential is algebraically the least. 

In this book standard electrode (reduction) potentials will be employed, as recommended by the I.U.P.A.C. Table 8.1 f gives a list of such potentials. The reactions are written as reduction processes, e.g., Cu + 2e" -> Cu, A table of standard oxidation potentials would simply reverse all of the signs and the corresponding reactions would be oxidations, e.g., Cu Cu " + 26 ,... 

The standard electrode potential at the above mentioned standard state conditions is denoted by °. For the MCAT, the values of the standard electrode (reduction) potentials will be given to you if you are required to solve such a question. Do not try to memorize those values. The standard electrode potentials are based on an arbitration with reference to standard hydrogen electrode. The standard hydrogen electrode potential is considered to be 0 volt. 

In general, the LUMO energy values are useful guidelines for compound or additive selection for anode additives, but it is necessary to test the additive compound in practical cell experiments in order to examine the details of the coating film for topochemical reaction. These tests provide important information for the development of the functional electrolytes. Figure 19.14 shows the relationship of the LUMO energy values and reduction potentials of additives on NG or Pt electrode. Reduction potential on NG is higher than those on Pt electrode due to the... 

Measurement of Standard Single Electrode Reduction Potentials... 

The single electrode reduction potentials are measured with respect to the SHE. The SHE, which is based on the reaction, 2H+ + 2e -o- H2 on platinized platinum, is assigned the reduction potential of zero when the activity of the hydrogen ion is unity and the pressure of H2 is 1 atm. Figure 4.1.6 illustrates the schematic for measuring the standard single reduction potential of Cu /Cu and Zn /Zn systems. 

Another way of understanding this is to look at the oxidation potential of both bromide and choride ions. Oxidation potentials are the electrode (reduction) potentials with the sign reversed. 

The potential of these half-cell reactions can be determined by comparison with the hydrogen electrode all under standard conditions, which is unit concentration for ions in solution and 1 atm pressure for gases at 25°C. The value of these standard electrode reduction potentials is given in Table 9.4. The standard cell potential of reaction (9.15) is... 

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