Electrolyte solutions
The first satisfactory theory of ionic solutions was that proposed by Arrhenius in 1887, who was able to bring together the results of diverse investigations into broad generalization known as the theory of electrolytic ion. Although the theory proved quite useful for describing weak electrolytes, it was soon found unsatisfactory for strong and moderately strong electrolytes.
Accordingly, many attempts were made to modify or replace Arrhenius s ideas with better ones, and finally, in 1923, Debye and Hückel put forth a new theory. It is based on the principles that strong electrolytes are completely dissociated into ions in solutions of moderate concentration and that any deviation from complete dissociation is due to interionic attractions.
Properties of solutions of electrolytes
Electrolysis
When, a direct electric current (dc) of several volts flows through an electrolytic cell (Figure 6-1), a chemical reaction occurs. The process is known as electrolysis. Electrons enter the cell from the battery or generator at the cathode (road down); they combine with positive ions or cations in the solution, and the cations are accordingly reduced. The negative ions, or anions, carry electrons through the solution and discharge them at the anode (road up), and the anions are accordingly oxidized.
Reduction is the addition of electrons to a chemical species, and oxidation is removal of electrons from a species. Reduction occurs at the cathode, where electrons enter from the external circuit and are added to a chemical species in solution. Oxidation occurs at the anode, where the electrons are removed from a chemical species in solution and go into the external circuit.
In the electrolysis of a solution of ferric sulfate in a cell containing platinum electrodes, a ferric ion migrates to the cathode, where it picks up an electron and is reduced: