Conduction in Solution—a Review

In metals, current flow is due to electron motion. This is not the case in electrolytic solution here a potential difference leads to net ionic migration. It is the motion of the ions which accounts for charge transfer in solution. 

For consideration of ionic conduction in solution. Ohm s law is most conveniently formulated in a form analogous to the transport equations presented in Section 2.4, 

Here j is the current density, or equivalently, the charge flux. The electric field E, which is the gradient of the potential p, provides the driving force for conduction. The transport coefficient a is the specific conductivity, expressed in ohm m k While (3.1) may appear unfamiliar, it reduces to the common expression I — VjR in the special case of conduction in a wire of uniform cross section (see Problem 3.1). 

To relate the transport coefficient a to the properties of the solvated species requires recognizing that even pure solvent contains some ions. Thus, the results of conductivity measurements are corrected for the specific conductivity of the cell in the absence of electrolyte, the conductivity attributed to electrolyte is then 

Electrolytic conduction is due to the presence of ions thus (T is a function of the concentration of equivalents of ions, Strong electrolytes like NaCl, HNOg, etc., are fully dissociated while weak electrolytes like HCN are not. In the former case C is the same as the normality of the electrolyte C in the latter it is not. As a consequence the conductivity of a strong electrolyte is roughly proportional to C while that of a weak one is not. It is convenient to define the equivalent conductance which accounts for the concentration dependence 

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