Recently we have proposed a new mechanism describing the borohydride oxidation reaction (BOR) on gold electrode. Despite its apparent simplicity, this mechanism, which consists of one E step and one Electrochemical Adsorption Reaction step (E-EAR) deserves to be studied for its own. The Faradaic impedance of one-step reactions involving adsorbed and soluble species has been studied in the past. Multistep mechanisms have also been under focus, but theoretical studies remain scarce, and they often rely on oversimplistic assumptions (e.g. fast mass transport). Once recalled the basics of Faradaic impedance calculation for an electrochemical reaction, the paper will describe how difficult the interpretation of Faradaic impedance diagrams can be when the reaction involves both adsorbed species and mass transport limitation for soluble species. The paper introduces a method to interpret the theoretical graphs of Faradaic impedance. (C) 2013 Elsevier B.V. All rights reserved.