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The molar ionic conductivity of each ionic species is proportional to its electrical mobility (μ), or drift velocity per unit electric field, according to the equation =, where z is the ionic charge, and F is the Faraday constant. [9]
In practice the molar ionic conductivities are calculated from the measured ion transport numbers and the total molar conductivity. For the cation + = + +, and similarly for the anion. In solutions, where ionic complexation or associaltion are important, two different transport/transference numbers can be defined.
Conductivity or specific conductance of an electrolyte solution is a measure of its ability to conduct electricity. The SI unit of conductivity is siemens per meter (S/m). Conductivity measurements are used routinely in many industrial and environmental applications as a fast, inexpensive and reliable way of measuring the ionic content in a ...
In fact, conductivity measurements show that ionic mobility increases from Li + to Cs +, and therefore that Stokes radius decreases from Li + to Cs +. This is the opposite of the order of ionic radii for crystals and shows that in solution the smaller ions (Li + ) are more extensively hydrated than the larger (Cs + ).
The molar ionic strength, I, of a solution is a function of the concentration of all ions present in that solution. [3]= = where one half is because we are including both cations and anions, c i is the molar concentration of ion i (M, mol/L), z i is the charge number of that ion, and the sum is taken over all ions in the solution.
Electrical conductivity of water samples is used as an indicator of how salt-free, ion-free, or impurity-free the sample is; the purer the water, the lower the conductivity (the higher the resistivity). Conductivity measurements in water are often reported as specific conductance, relative to the conductivity of pure water at 25 °C.
The second law (1833) established the proportionality between Δm and the “electrochemical equivalent” and defined the Faraday constant F as F = (Δq/Δm)(M/z), where M is the molar mass and z is the charge of the ion. In 1834, Faraday discovered ionic conductivity in heated solid electrolytes Ag 2 S and PbF 2. [4]
The Ostwald law of dilution provides a satisfactory description of the concentration dependence of the conductivity of weak electrolytes like CH 3 COOH and NH 4 OH. [3] [4] The variation of molar conductivity is essentially due to the incomplete dissociation of weak electrolytes into ions.