Calculation of Stationary Electrode Polarograms for Cases of Reversible Chemical Reactions Other than First-Order Reactions Following a Reversible Charge Transfer Mark S . Shumanl Department of Chemistry, Texas Christian University, Fort Worth, Texas 76129
THETHEORY of stationary electrode polarography has recently been extended to include irreversible second-order reactions following electron transfer (1-4). The main emphasis of these studies has been to relate polarograms to the kinetic parameters of the coupled chemical reactions. Whenever following reactions arb rapid and reversible and therefore diffusion controlled, kinetic information cannot be obtained. Nevertheless, a unique current-potential curve should result from each stoichiometry. The work presented here is the 1 Present address, Department of Chemistry, Whitman College, Walla Walla, Washington 99362
(1) . , J. M. Saveant and E. Vianello, Electrochim. Acta,. 12,. 1545 (1967). (2) M. L. Olmstead, R. G. Hamilton, and R. S. Nicholson, ANAL. CHEM.,41, 260 (1969). (3) M. Mastragostino, L. Nadjo, and J. M. Saveant, Electrochim. Acta, 13, 721 (1968). (4) M. L. Olmstead and R. S. Nicholson, ANAL.CHEM.,41, 862 (1969).
calculation of current-potential curves for cyclic voltammetry and the general reaction 0 ne- e R (1) mR qZ where 2 is electroinactive and assumed to be in rapid, reversible equilibrium with R,and where m and q are stoichiometric coefficients and n is the number of electrons. An equilibrium constant K = [ZIa/[R]"is defined for the chemical reaction and it is assumed that the equilibrium favors 2. The limits of applicability of the above assumptions were not investigated here, but limits for the case of a dimerization (m = 2, q = 1) have been given elsewhere (I).
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CALCULATIONS The equation used for calculation of current-voltage curves is obtained by simple modification of Equation 16, Reference (5) which applied to the reaction ( 5 ) M. S. Shuman, ANAL.CHEM.,p 142.
Table I. Current Functions d & ( a r ) OfneeR 3ReZ
