The chemical activities of Ox- and Red-forms are diminishing in opposite directions in the electrochemical series1-4. It was concluded, that a chemical equilibrium of conjugated forms takes place in the center of the series5. The direction of spontaneous half-reactions, leading to formation of double layers, is due to instability of Red- or Ox-forms, since the energy of formation the intermediate bound electrons neinterm in them is const5-7.The transfer from the pair of weak metal - copper Cu ( Eo Cu2+/Cu = + 0.34 V SHE1-4) to the pair of weak non-metal- iodine I2 ( Eo I-/I2 = + 0.535 V SHE1-4 ) is in the center of the series. In formal half - reaction of reductions Cu2+ + 2e = Cu, ions Cu2+ are stable in solutions, copper has some metal activity8. In formal reduction half-reaction ½ I2 + einterm = I-, iodine has non-metal activity and ions I- are stable in solutions8. Hence, spontaneous half-reactions of oxidation Cu → Cu2+ + 2einterm and reduction ½ I2 + einterm → I- take place. Thus, the chemical equilibrium of Red- and Ox-forms in half-reaction is between these spontaneous half-reactions at the average potential ~+0.44 V SHE.The different pairs Men+/Me and Mem+/Me of not active metals (Cu, Ru, Te, Po) are in the same center of the series1-4. These pairs have the close standard potentials: Eo Cu2+/Cu = + 0.34 V SHE1-4 and Eo Cu+/Cu = + 0.52 V SHE1-3; Eo Ru2+/Ru = + 0.455 V SHE2,3 and Eo R u3+/Ru= + 0.38 V SHE2; Eo Te2+/Te= +0.40 V SHE2 and Eo Te4+/Te = +0.568 V SHE2,3; Eo Po2+/Po = = +0.368 V SHE1,2 and Eo Po4+/Po = + 0.73 V SHE1 (+0.775V SHE2; +0.76 V SHE3). Hence, the pairs Men+/Me and Mem+/Me of each metal should have the potential determining ions with the close energy formation in solutions. However, these ions are also known as thermodynamic stable and unstable in solutions (for example, Cu2+ and Cu+; Ru2+, Ru3+ and Ru4+; Te2+ and Te4+; Po2+ and Po4+)8. Hence, their spontaneous oxidation and reduction half-reactions (due to instability of metal or its ions) take place by both sides from the chemical equilibrium. The average potential calculated by the sum of these standard potentials is equal + 0.472 V SHE (+0.477 V SHE).Moreover, the standard potentials of the redox pairs Men+ / Mem+ formed by different ions of these metals are also close to their Eo Men+/ Me and Eo Mem+/Me ( Eo Cu2+/Cu+ = +0.159 V SHE 1-3; Eo Ru3+/Ru2+ = +0.249 V SHE1-3; Eo Ru4+/ Ru3+ = +0.49 V SHE9; Eo Te4+/ Te2+= +0.736 V SHE, calculated by Latimer equation; Eo Po3+/Po2+ = +0.330 V SHE2; Eo Po4+/Po2+ = + 0.9 V SHE3). The average potential found from the sum of these verified redox potentials is equal to +0.477 V SHE. The standard potentials Eo of such pairs are differed for more active metals (for example, Eo Fe 3+ / Fe = - 0.037 V SHE, Eo Fe 2+ / Fe = - 0.473 V SHE, Eo Fe 3+ /Fe +2 = + 0.771 V SHE)1-4.The closeness of the standard potentials Eo of the pairs Men+/Me, Mem+/Me and Men+/Mem+ pairs exists only for weak active metals and non-metal which outer electrons are not b...

The Distribution of Electrodes by the Standard Potentials A.I.Chernomorskii (Scientific Resources Co) e-mail: sciresources@aol.com The distribution of electrodes (Ox/Red-pairs) by their standard potentials with the maximum number of electrodes with Eo ~ +0.5 V SHE was shown in [1,2]. The distribution was carried on the listings included ~400 ÷ 700 half-reactions [3-6]. The standard potentials for ~2000 half-reactions have been reported up to now [7,8,9]. It was arranged 1807 half-reactions including in the listing [9] in terms of their standard potentials by finding the number of half-reactions with the standard potentials in intervals 0.1÷ 0.2 V from -3.1 to +3.1 V SHE. The average value of potential was assigned to each of these intervals. Then we plotted the distribution curve (Fig.1). The distribution was carried by the use computer program. One can see from Fig.1 that the number of half-reaction increases as one approaches the center of the electrochemical series. The distribution maximum occurs at a standard potential of +0.45 V SHE (if intervals are 0.1 V) and +0.47 V SHE (if intervals are 0.14 V SHE). These potentials of the maximum are close to the Billiter potential +0.475 V SHE [10, 11]. Fig. 1. The distribution law of half-reactions by their standard potentials. The intervals of finding 0.1 V. The potential of the maximums is + 0.45 V SHE Thus, it follows from the distribution obtained (Fig.1) that electrode Ox/Red-pairs in this center of the electrochemical series have lower oxidation and reduction activity than the redox pairs with more positive and more negative potentials, respectively. Hence, these pairs are neither active oxidants nor active reductants. It can be suggested that their both conjugated Ox- and Red-forms would have close energy states. However, this is valid if half-reactions are analyzed as the definite chemical interactions of Ox/Red-pairs with water molecules on electrodes. Electrons neinterm with the definite non-specific electrostatic bond with Ox-forms should be formed Red → Ox + neinterm or consumed Ox + neinterm → Red in these interactions which lead to formation of the electric double layers and outer potential jumps in them on electrodes [12-14]. It takes into account that half-reactions of elements transition from metals to non-metals (for example, Eo Te2+/Te = = +0.40 V SHE; Eo Te4+/Te = +0.568 V SHE; Eo I/I - = +0.535 V SHE) are in maximum of the distribution. It can be concluded some hypothetical electrode form between metals and non-metals (characterized by the potential ~+0.47 V SHE of maximum of the distribution) with the non-specific intermediate bounded outer electrons neinterm. Such a form (neither metal nor non-metal) would not have own oxidation and reduction activity. The potential of the maximum ~+0.47 V SHE should characterize this inactive electrode form with non-specific bound outer electrons. The electron work function of non-specific bounded electrons neinterm is found to be equal 5.18-5.19 eV [12-14]. There is suggested the exponential probability e – ΔE/const of the formation of specific electron bonds in acts Ox + neinterm → Red, where ΔE is the changes of energy at the formation of specific electron bonds at accepting non-specific bound electrons neinterm. Accordingly, the probability of formation of specific electron bonds in Red-forms should exponentially decrease with the increase of energy of their formation ΔE. It is concluded, that the number of existed Red-forms (and conjugated Ox-forms) with increased ΔE should also decrease exponentially. References (1) A.I. Chernomorskii, Russ.J. Electrochemistry, 1979, 15, 1347. (2) A.I. Chernomorskii, Dokl.Akad.Nauk Uzb.SSR, 1977,10, 33-35. (3) N.E. Khomutov, in: Results of Science, Electrochemistry, 1964 (in Russian), VINITI, Moscow (1966), p.7. (4) B.P.Nicol'skii (editor), Chemist's Handbook, Second edition, Vol.3 [in Russian], Khimiya, Moscow-Leningrad (1964). (5) M Pourbaix, Atlas d’Équilibres Électrochimuque, Gathier-Villars, Paris (1963). (6) W. M. Latimer, The Oxidation States of the Elements and Their Potentials in Aqueous Solutions, Prentice-Hall, New York (1952). (7) Handbook in Electrochemistry (A.M.Sukhotin, editor), 1981 (in Russian), Khimiya, Leningrad, pp.124 - 154. (8) S.G.Bratsch, J.Phys.Chem.Data, 1989,18, 1, pp. 1-21. (9) Ya. I.Tur'yan, Redox-reactions and potentials in analytical chemistry, Khimiya, Moscow, 1989, pp.177-233. (10) J. Billiter, Z. Electrochem, 1931,37, 8/9,736-740. (11) K.J. Vetter,”Electrochemical Kinetics”(Translated into Russian),Izd.Khimiya, Moscow,1967, p.116. (12) A.I.Chernomorskii, Russ. J. Phys.Chem., 1978, 52, 757; 1981,55,474. (13) A.I Chernomorskii, Thermodynamics of electrodes, FAN, Tashkent,1993, p. 184. (14) A.I Chernomorskii, The intermediate electron bond and half-reactions, Scientific Resources, N-Y,1999. Figure 1

No abstract

The Latimer equation1 defines the relation between the standard potentials of metal electrodes Eo Me n + / Me , Eo Me n + / Me m + and redox electrode Eo Me n + / Me m +, where n, m, n - m are number of electrons taken part in half-reactions of metal and redox electrodes Eo Me n + / Me m += (nEo Me n + /Me - mEo Me m + /Me) / n-m (1)The Eqn.(1) can be envisaged as (ψo Me n + / Me m + - const) = [n (ψo Me n + /Me - const) - m (ψo Me m + /Me - const)] / n-m (2) n - m (ψo Me n + / Me m +)- n const + m const = n ψo Me n + /Me - n const - m ψo Me m + /Me + m const (3) ψo Me n + / Me m + = (n ψo Me n + /Me - m ψo Me m + /Me ) / n-m (4)where ψo Me n + /Me, ψo Me m + /Me andψo Me n + / Me m +, are respectively the potential drops in double layers on metal electrodes and on redox electrode, const is the potential drop in double layer on the standard hydrogen electrode.The difference nEo Me n + /Me - mEo Me m + /Me in the nominator of the Latimer equation (Eqn. 1,2) includes the difference (-nconst + mconst), i.e., const is not excluded (n ≠ m). However, const is excluded from the difference Eo Me n + / Me - Eo Me m + / Me = (ψo Me n + /Me - const) - (ψo Me m + /Me - const) = ψo Me n + /Me - ψo Me m + /Me. It was compared the absolute (not relative) differences Eo Me n + / Me - Eo Me m + / Me = ψo Me n + /Me – ψo Me m + /Me and the corresponded Eo Me n + / Me m + for redox electrodes (Fig.1). The differences Eo Me n + / Me - Eo Me m + / Me are linearly decreased with the decrease of the negative and positive standard potentials of redox pairs Eo Me n + / Me m +. These linear relations take place mostly for redox pairs which conjugated ions have equal or similar electron structures and equal n - m (for example, Pb4+/Pb2+, Te4+/Te2+, Po4+/Po2+; Ga3+/Ga2+, In3+/In2+). For other redox pairs, equal changes of charges of ions at some similarity of their electron structures defines also the linear decrease of differences Eo Me n + /Me - Eo Me m + / Me against Eo Me n + / Me m + (for example, Tl3+/Tl+, Fe3+/Fe2+). The extrapolation of these linear relations to Eo Me n + / Me - Eo Me m + / Me = ψo Me n + /Me - ψo Me m + /Me = 0 leads to the potential Eo Me n + / Me m + = ~ + 0.47 V SHE on the Eo Me n + / Me m +- axis that is close to the Billiter potential +0.475 V SHE2. Some of these linear relation intersect directly the Eo Me n + / Me m +- axis at Eo Me n + / Me m + = +0.47 V SHE (Fig.1). Other linear relations are united at the comparison of the absolute differences | Eo Me n + / Me - Eo Me m + / Me | and the corresponded Eo Me n + / Me m + (Fig.2).Analyzing Eqn.(4), it is concluded that there should be proportionalities ψo Me n + /Me m + = (n ψo Me n + /Me - m ψo Me m + /Me ) / n - m = k (ψo Me n + /Me - ψo Me m + /Me) = k (Eo Me n + / Me - Eo Me m + / Me), (5)where k are coefficients for similar redox electrodes (Fig.1). Hence, when Eo Me n + / Me - Eo M...

No abstract