23. THEORY OF ELECTROLYTIC DISSOCIATION.

Solutions of all substances can be divided into two groups: electrolytes - carry electric current, nonelectrolytes conductors are not. This division is conditional because all solutions of substances carry electric current, all of them are to some extent dissolved in water and break up to cations (positively charged ions) and anions (negatively charged ions). It is necessary to distinguish the real and potential electrolytes.
The real electrolytes are in the form of ions already in individual state i.e. before they are melted or transferred to solution. All typical salts which in solid state form ionic crystal lattice belong to the real electrolytes (for example NaCl, _K2SO4, etc.)
Potential electrolytes do not contain in individual condition of ions, but form them upon transition of substance to solution. The substances consisting of molecules with strongly polar bonds concern to them (for example HCl).
The most part of organic compounds, for example diethyl ether, benzene, glucose, sucrose belongs to nonelectrolytes.
Charged particles appear only in solutions and fusions of substances owing to electrolytic dissociation. Electrolytic dissoatsiation-it process of disintegration of substances on ions at dissolution or fusion.
Therefore, as a result of dissociation in solution there are ions which are premises for emergence in solution or fusion of such physical property as electric conductance.
How there is dissolution process?. Destruction of ionic crystal lattice happens under bite, for example waters. Polar water molecules so reduce forces of electrostatic attraction between ions in crystal lattice that ions become free and pass into solution.
At fusion when there is heating of crystal, ions begin to make intensive fluctuations in nodes of crystal lattice therefore it collapses, formed fusion which consists of ions.
The theory of electrolytic dissociation was created in 1884-1887 by the Swedish chemist Arrhenius. This classical theory has allowed both electric conductance of fusions and solutions, and course of chemical reactions in solutions between melted or solutes.

Scheme of electrolytic dissociation.

Water molecules are dipolar, i.e. one end of molecule is loaded negatively, another - is positive. The molecule negative pole approaches sodium ion, positive - chlorine ion; surround ions from all directions and pull out from crystal, and, only from its surface
The equation of dissociation can be written down as follows:

NaCl Na + + Cl-

Electrolytic dissociation is caused not only by water, but also non-aqueous polar solvents, such as Liquid ammonia and liquid sulfur dioxide. However property to weaken electrostatic attraction between ions in lattice is characteristic of water it is expressed especially brightly.
The free ions which have appeared in aqueous solution are surrounded with polar water molecules: around ions the hydrated cover is formed, i.e. hydration process proceeds.

Force of electrolytes.

Force of electrolytes can be characterized by means of extent of dissociation.
Extent of dissociation of electrolyte is private from division of number of the pro-dissociated molecules to total number of molecules of the electrolyte entered into solution.

Extent of dissociation of potential electrolytes changes within 0 <α ≤1 (value α=0 belongs to nonelectrolytes).
Extent of dissociation increases at increase in dilution of solution, and also at temperature increase (temperature increase leads to increase in kinetic energy of the dissolved particles that promotes disintegration of molecules on ions.)
Force of electrolytes in aqueous solution is defined by their extent of dissociation at constant concentration and temperature. Treat strong electrolytes substances belong extent of dissociation of which is close to 1. Soluble alkalis, salts, acids treat them kindly.

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