Chemical changes solution conductivity

Since in the interconversion of electrical and chemical energies, electrical energy flows to or from the system in which chemical changes lake place, it is essential that the system be. in large part, conducting or consist of electrical conductors. These are of two general types—electronic and electrolytic—though some materials exhibit both types of conduction. Metals are the most common electronic conductors. Typical electrolytic conductors are molten salts and solutions of acids, bases, and salts. 

The solutions are nonconducting, and the compounds display no tendency to undergo chemical reactions (hydrolysis, polymerization, etc.). However, as shown later, heating these compounds in the presence of donor reagents causes significant changes in most of their properties (NMR spectra, chemical activity, electrical conductivity, etc.), thus making them similar in properties to the typical dynamic allylic compounds. 

ELECTROLYSIS, THE NATURE OF ELECTROLYTIC CONDUCTANCE, IONS Chemically pure water practically does not conduct electricity, if however, as already stated, acids, bases, or salts are dissolved in it, the resultant solution not only conducts the electric current, but undergoes chemical changes as well. The whole process is called electrolysis. 

Rates and products of solvolytic reactions (equation 1) were obtained by standard NMR or high-performance liquid chromatographic (HPLC) methods. Rates of reactions were also monitored from the appearance of acid (HX, equation 1), determined by the change in conductance of the solution or by titrimetric methods. For anions X- containing a suitable chromophore, reaction rates were monitored by the change in UV spectrum of the solution. The chemicals required for this study were either... 

In either method, the time-resolution characteristics of the instruments employed must be sufficient to detect and follow the property change. Examples of physical properties measured in such applications include intensity of transmitted, scattered, or absorbed light (Tanaka et al. 1979 La Mer and Dinegar 1951), solution conductivity (Sohnel and Mullin 1978), heat released (Nyvlt and Pekarek 1980), light emission (Garten and Head 1963), and chemical composition of the solution (Packter 1974 Koutsoukos and Kontoyannis 1984). 

The dissolution of an ionic salt is an example of physical change, since the ions are present in both solid salt and in solution. By definition, covalent substances contain no ions, but some covalent substances may produce ions as a result of their chemical reaction with water. The presence of such ions may be confirmed by testing the solution to see if it conducts electricity, but it is the new reactions of the solution - the reactions of the ions produced - that conclusively prove that chemical change has taken place. We now look at three important examples the reactions with water of hydrogen chloride, pure sulfuric acid and ammonia. 

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