Standard Reduction Potentials in Aqueous Solution at

Table 16.1 Standard Reduction Potentials in Aqueous Solution at 25 °C...

Practically in every general chemistry textbook, one can find a table presenting the Standard (Reduction) Potentials in aqueous solution at 25 °C, sometimes in two parts, indicating the reaction condition acidic solution and basic solution. In most cases, there is another table titled Standard Chemical Thermodynamic Properties (or Selected Thermodynamic Values). The former table is referred to in a chapter devoted to Electrochemistry (or Oxidation - Reduction Reactions), while a reference to the latter one can be found in a chapter dealing with Chemical Thermodynamics (or Chemical Equilibria). It is seldom indicated that the two types of tables contain redundant information since the standard potential values of a cell reaction ( n) can be calculated from the standard molar free (Gibbs) energy change (AG" for the same reaction with a simple relationship... 

TABLE 1.1 STANDARD REDUCTION POTENTIALS IN AQUEOUS SOLUTION AT 25°C... 

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

Before we discuss standard electrode potential, we will talk about electromotive force (emf). The electromotive force of a cell is the potential difference between the two electrodes. This can be measured using a voltmeter. The maximum voltage of a cell can be calculated using experimentally determined values called standard electrode potentials. By convention, the standard electrode potentials are usually represented in terms of reduction half-reactions for 1 molar solute concentration. The standard electrode potential values are set under ideal and standard-state conditions (latm pressure and 25°C temperature). From the MCAT point of view, you can assume that the conditions are standard, unless stated otherwise. Table 12-1 shows a list of standard electrode potentials (in aqueous solution) at 25°C. 

Table A5.6 gives selected values for standard reduction potentials at T = 298.15 K. The values were taken from W. M. Latimer, The Oxidation States of the Elements and their Potentials in Aqueous Solutions, Second Edition, Prentice-Hall, Inc., Engelwood Cliffs, N.J. (1952).

In aqueous solution, primary interest centers on the production of CO, formic acid, methanol and alcohols, and methane and hydrocarbons. The standard redox potentials (versus the saturated calomel electrode, SCE) for the common C02 reduction products of formic acid, CO, formaldehyde, methanol, and methane in aqueous solution at pH 7.0 are given as [42] ... 

Standard Reduction Electrode Potentials for Inorganic Systems in Aqueous Solutions at 25°C... 

A few elements—C, N, O, S, Fe, Mn—are predominant participants in aquatic redox processes. Tables 8.6a and 8.6b present equilibrium constants for several couples pertinent to consideration of redox relationships in natural waters and their sediments. Data are taken principally from the second edition of Stability Constants of Metal-lon Complexes and Standard Potentials in Aqueous Solution (Bard et al., 1985). A subsidiary symbol pe (W) is convenient for considering redox situations in natural waters. pe°(W) is analogous to pe except that H" and OH in the redox equilibrium equations are assigned their activities in neutral water. Values for pe°(W) for 25 °C thus apply to unit activities of oxidant and reductant at pH = 7.00. pe°(W) is defined by... 

State may be considered to contain Ru(III), two bpy and one [bpy] . The singlet excited state rapidly decays to a triplet excited state, the lifetime of which in aqueous solution at 298 K is 600 ns, long enough to allow redox activity to occur. The standard reduction potentials in Fig. 22.24 show that the excited [Ru(bpy)3] + state is both a... 

By international agreement, a standard electrode potential, E", measures the tendency for a reduction process to occur at an electrode. In all cases, the ionic species are present in aqueous solution at unit activity (approximately 1M), and gases are at 1 bar pressure. Where no metallic substance is indicated, the potential is established on an inert metallic electrode, such as platinum. 

All M cations of this triad are diamagnetic and, unless coordinated to easily polarized ligands, colourless too. In aqueous solution the Cu ion is very unstable with respect to disproportionation (2Cu v - Cu + Cu(s)) largely because of the high heat of hydration of the divalent ion as already mentioned. At 25°C, K (= [Cu ][Cu ]-2) is large, (5.38 0.37) x 10 1mol , and standard reduction potentials have been calculated to be ... 

---