Conductance and Conductivity of an Electrolyte

As we can see from Equations 3.5 and 3.6, conductance is proportional to the number densities (concentrations) of the ions,and their ionic conductivities X, and the proportionality factor is (A/l). Therefore, at constant composition of the electrolyte, if the conductor cross section is larger and/or the distance between electrodes is shorter, then the conductance is larger and resistance is smaller. To finalize the description of the relationships between conductance, conductivity, resistance, and resistivity, the following equations might be useful  

FIGURE 3.10 A glass tube with an electrolyte solution inside. The length of the tube is I, and its cross section is A. Two electrodes should be attached at each end of the tube to provide an electric field moving the ions. 

In electrochemical science and engineering, we are interested in lx)th measuring and calculating the conductivity of a variety of ion conductors. The experimentally measured conductivities for a variety of materials can be found in [2], As can be seen from Table 3.1, where some examples for commonly used in elechochemical science and engineering materials are given, the conductivity can vary by many orders of magnitude. 

In calculating the conductivity of an electrolyte solution, the following problems can arise (1) difficulties in estimating the concentration of ions due to the association/ dissociation processes, (2) absence of the ionic conductivities for some ions, (3) the cell geometry (/ and A) is not always well defined. Still, the conductivity of very pure water can theoretically be calculated and this calculation is absolutely reliable. 

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