Читать книгу Electroanalytical Chemistry - Gary A. Mabbott - Страница 16

In many instrumental electrochemical methods, an electrode surface – usually a metal or carbon conductor – exchanges electrons with the analyte. In those cases, the electrode is treated as an inert source or sink for the electron exchange. The electrode does not appear in the reaction equation. Instead, the electrode reaction appears to be the same as the half reaction for the species being converted. A major benefit of using electrodes in place of a reagent in solution is the fact that the current passing through the electrode can be measured unlike the situation when two chemical species in solution exchange electrons directly. Furthermore, the current is a measure of the amount of analyte reacting. Whenever electrons are transferred between the analyte and an electrode, the current can be integrated with respect to time in order to obtain the charge, Q, transferred.

(1.10)

This charge is related to the moles of oxidized or reduced species by Faraday's law:

(1.11)

where n = number of moles of electrons transferred per mole of reactant, N is the number of moles of the same reactant that undergo conversion, and F is Faraday's constant, 9.6485 x 10⁴ C/mol of electrons.