On electrolytes and nonelectrolytes of substance are divided by their ability to carry electric current. At dissolution or fusion, electrolytes carry current, and nonelectrolytes do not.
What substances are electrolytes and nonelectrolytes
Carry to electrolytes acids, the bases and salts. In their molecules there are ionic or covalent strongly polar bonds. Carry to nonelectrolytes, for example, hydrogen, oxygen, sugar, benzene, air and many other organic matter. At molecules of these substances there are covalent low-polar and unpolar bonds.
Theory of electrolytic dissociation of S. Arrhenius
The theory of electrolytic dissociation created by S. Arrhenius in 1887 allows to explain conductivity of solutions and fusions of electrolytes. The fact is that molecules of acids, salts and bases at dissolution or fusion break up to ions – positively and negatively charged. This process is called dissociation, or ionization.
Ions in itself in solution or fusion move chaotically. Besides, besides dissociation there is at the same time also an opposite process – connection of ions to molecules (association, or a molyarization). From this it is possible to draw a conclusion that dissociation is reversible. At transmission of electric current through solution or fusion of electrolyte the positively charged ions begin to move to a negatively charged electrode (cathode), and negatively charged – to positively charged (anode). Therefore ions of the first type were called "cations", and the second type – "anions". Ions of metals, a hydrogen ion, an ammonium ion, etc. can be cations. As anions, hydroxide ion, ions of the acid remains and others act.
Extent of dissociation, strong and weak electrolytes
Various electrolytes in water solutions can break up to ions completely or not completely. The first call strong electrolytes, the second – weak. The number showing what part from the total number of the dissolved molecules dissociated on ions is called extent of dissociation α.Сильные electrolytes - it is strong acids, all salts and the soluble bases in water – alkali. Strong acids are chloric, chlornovaty, sulfuric, nitric, salt, bromovodorodny, yodovodorodny and some other. Hydroxides of alkaline and alkaline-earth metals – lithium, sodium, potassium, rubidium, caesium, calcium, strontium and barium belong to alkalis.