A theoretical treatment of electrode reactions preceded by a first-order chemical reaction under chronopotentiometric conditions with an exponential time current at spherical electrodes of any size has been developed. The general rigorous solution obtained allows us to study, without any limitations, the CE mechanism response and the influence of kinetic rate constants, chemical equilibrium constant, electrode sphericity and the applied current. Analytical solutions applicable under kinetic and total steady state conditions are also shown to be special cases of the general solution presented here. The analysis of appropriate working curves leads us to obtain accurate values of the rate constant of the chemical reaction. (C) 2010 Elsevier B.V. All rights reserved.