ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
In previous work [J. Keizer, J. Chem. Phys. 82, 2751 (1985)] we used statistical nonequilibrium thermodynamics to predict a non-Nernstian component to the electromotive force (EMF) for half-reactions involving reactants at nonequilibrium steady states. In this paper we present a simple theory for calculating the nonequilibrium component of the EMF based on the elementary transport processes occurring in a continuously stirred tank reactor (CSTR). The calculations utilize the density–density correlation function, which is obtained from the statistical theory of nonequilibrium thermodynamics. This gives rise to an expression for the second partial derivatives of the generalized entropy, or sigma function, which is used to calculate generalized chemical potentials. The generalized chemical potentials are related to the EMF through a generalization of the Nernst equation. The calculations presented here depend on the residence time in the CSTR, reaction rate constants, feed line concentrations in the CSTR, and the diffusion constants of reactants and products. A characteristic diffusion length is used to represent the length scale below which turbulent mixing effects are not important. Calculations with the theory are carried out for several different reaction mechanisms, including A+B(arrow-right-and-left)C; A+B(arrow-right-and-left)C, D+E(arrow-right-and-left)B; A+B(arrow-right-and-left)2B; and A+B→C+D, A+D→C+E. Values of the nonequilibrium EMF depend on the mechanism as well as all of the transport parameters cited above. For a plausible choice of the diffusion length, corrections to the Nernst formula can be as large as 10–15 mV. Specific calculations for the reaction of Fe2+ with S2O2−8 are shown in the preceding paper to agree with experimental measurements on this system in a CSTR.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.452912
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