Electrolyte solutions, conductance

Fig. 11-1. A strong electrolyte solution conducts better than a weak electrolyte solution.

In a Daniell cell, the pieces of metallic zinc and copper act as electrical conductors. The conductors that carry electrons into and out of a cell are named electrodes. The zinc sulfate and copper(II) sulfate act as electrolytes. Electrolytes are substances that conduct electricity when dissolved in water. (The fact that a solution of an electrolyte conducts electricity does not mean that free electrons travel through the solution. An electrolyte solution conducts electricity because of ion movements, and the loss and gain of electrons at the electrodes.) The terms electrode and electrolyte were invented by the leading pioneer of electrochemistry, Michael Faraday (1791-1867). 

Another important parameter related to electrolyte solution conductivity is the transport number t,-. This is defined as the fraction of the current carried by species i. On the basis of equation (6.7.4), it is clear that t,- is given by... 

Pure water does not conduct electricity. An nonelectrolyte solution does not conduct electricity / An electrolyte solution conducts electricity. ... 

Weak acids are classified as weak electrolytes, and the resulting solutions—called weak electrolyte solutions—conduct electricity only weakly. Figure 4.14 sununarizes the electrolytic properties of solutions. 

Ionic conductors arise whenever there are mobile ions present. In electrolyte solutions, such ions are nonually fonued by the dissolution of an ionic solid. Provided the dissolution leads to the complete separation of the ionic components to fonu essentially independent anions and cations, the electrolyte is tenued strong. By contrast, weak electrolytes, such as organic carboxylic acids, are present mainly in the undissociated fonu in solution, with the total ionic concentration orders of magnitude lower than the fonual concentration of the solute. Ionic conductivity will be treated in some detail below, but we initially concentrate on the equilibrium stmcture of liquids and ionic solutions. 

Electrogenerated conducting polymer films incorporate ions from the electrolyte medium for charge compensation (182). Electrochemical cycling in an electrolyte solution results in sequential doping and undoping of the polymer film. In the case of a -doped polymer, oxidation of the film results in the... 

Soluble corrosion products may increase corrosion rates in two ways. Firstly, they may increase the conductivity of the electrolyte solution and thereby decrease internal resistance of the corrosion cells. Secondly, they may act hygroscopically to form solutions at humidities at and above that in equilibrium with the saturated solution (Table 2.7). The fogging of nickel in SO2-containing atmospheres, due to the formation of hygroscopic nickel sulphate, exemplifies this type of behaviour. However, whether the corrosion products are soluble or insoluble, protective or non-protective, the... 

Electrolyte Solution a solution in which the conduction of electric current occurs by the passage of dissolved ions. 

When an ionic solid such as NaCl dissolves in water the solution formed contains Na+ and Cl- ions. Since ions are charged particles, the solution conducts an electric current (Figure 2.12) and we say that NaCl is a strong electrolyte. In contrast, a water solution of sugar, which is a molecular solid, does not conduct electricity. Sugar and other molecular solutes are nonelectrolytes. 

We have dealt with electrolysis before—every time we discussed or measured the electrical conductivity of an electrolyte solution. To see this, let s consider the processes that occur when we cause electric charge to pass through an aqueous solution of hydrogen iodide. 

A second characteristic property of metals is high electrical conductivity. The conductivity is so much higher than that of aqueous electrolyte solutions that the charge movement cannot involve the same mechanism. Again we find a... 

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