The Electrolysis of an Aqueous Salt Solution

For ionic crystals, such as sodium chloride, the increase in conductivity with increasing temperature can be represented by an exponential factor  

The value of E, which can be interpreted as the excitation energy required to move a sodium ion from its normal position in the crystal, is 190 kJ mole . The conductivity remains very low, about 1 X lO ohm cm , even at 800°C, only a degree below the melting point. 

Silver iodide is an example of a crystal with large ionic conductivity, which reaches the value 2.5 ohm cm at 555 C, 3° below the melting point. At the melting point the conductivity of the crystal is greater than that of the liquid. 

Although pure water does not conduct electricity very well (conductivity 4.4 X 10 ohm cm at 20°C). a solution of salt (or acid or base) is a good conductor. During electrolysis chemical reactions take place at the electrodes, as described below. 

The phenomena that occur when a current of electricity is passed through such a solution are analogous to those described in the preceding section for molten salt. The five steps are the following. 

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