Electrochemical Systems

Abstract

This chapter is devoted to substances called electrolytes, whose molecules dissociate in a solution into free ions. First, we derive the general form of the chemical potential of an electrolyte. Then we discuss briefly the Debye–Hückle limiting law and its implications. Next we introduce basic concepts and terminology related to aqueous solutions of acids and basis, such as a conjugate acid–base pair, pH of solution, the ion product of water and acid and base dissociation constants. In the next section, we discuss electrochemical cells, in particular, galvanic cells, in which chemical reactions are used to perform electrical work. To describe the operation of a galvanic cell in terms of thermodynamics, the concept of a reversible cell is introduced. This leads to the Nernst equation which relates the electric potential difference of the cell to the chemical reaction taking place in it. By measuring the cell potential it is possible to determine the equilibrium constant and the standard Gibbs free energy of the cell reaction, directly related to the standard chemical potentials of the reactants and products. Finally, we describe the standard hydrogen electrode which serves as a reference electrode.