to physical chemistry and biochemistry typical overall process in which particulate matter - molecules, ions (positively charged particles called cations and negatively charged particles, called anions) radicals disintegrate into smaller particles.This process is called dissociation, which is Latin for «dissociation» means "separation."It is characterized by such parameters as the "degree of dissociation," shows the ratio of dissociated to the total number of particles before the disintegration of the particles, ie the proportion of particles which disintegrated.The process of disintegration of the particles can occur as a result of certain actions on the matter, the nature of these effects determines the type of dissociation.There are thermal dissociation, photodissociation, dissociation under the influence of ionizing radiation, electrolytic dissociation.Dissociation is the opposite of association and recombination.This process is often confused with ionization.
electrolytic dissociation is a variety of dissociation takes place under the influence of polar molecules of the solvent and is chemical in nature.Substances which can dissociate in a solvent and ions conduct electricity are referred to as electrolyte (acid, salt, base).Substances which do not decompose when dissolved ions (alcohols, esters, carbohydrates, etc.) are not electrolytes.The most important solvent electrolytes - water.The water itself is characterized as a weak electrolyte.Polar solvents (e.g., ethanol, ammonia and acetic acid) are also capable of dissolving the electrolytes.Dissociation of acids, alkalis, salts like and dissociation occur in the aqueous solutions.Salts - a class of chemical compounds whose molecules are composed of positively charged particles (metal cations), and negatively charged (anionic acid residues).Acidic salts in contrast to the usual salts are composed of two types of cations (metal and hydrogen) and an acid anion residue.When dissolved in water, salt molecules dissociate into ions.Salt can be recovered evaporate the water.
There are strong and weak electrolytes.In the classical theory of electrolytic dissociation process recognized considered reversible, but this statement applies only to weak electrolytes in dilute solutions.An electrolytic dissociation of acids, bases, salts, is an irreversible process, since salt (virtually all except certain complex), acids and bases (those formed with alkali and alkaline earth metals) are strong electrolytes, and dilute solutions of the molecule entirely (100%) dissociated into ions.Strong electrolytes: NaCl (sodium chloride), HNO3 (nitric acid), HClO3 (chloric acid), CaCl2 (calcium chloride), NaOH (sodium hydroxide).Weak electrolytes: NH4OH (ammonium hydroxide), H2CO3 (carbonic acid), CH3COOH (acetic acid), and most organic acids and bases.They when dissolved in water can dissociate partially (typically, this value ranges from 1 to 10%).
Therefore, the assertion that the solution of a strong electrolyte contains only ions in a solution of weak electrolytes, mainly nondecomposed molecule substances.Dissociation of the salts leads to the fact that in the solution containing only metal ion and an acid residue (e.g., sodium cation, Na + and Cl- chlorine anion), and nondecomposed molecules (NaCl) have salt.Dissociation acid salts leads to the formation in solution of a metal cation, hydrogen cation and anion acid residue.For example, an acid salt NaHCO3 (sodium bicarbonate) dissociates into a sodium cation (Na +), a cation of hydrogen (H) and an anion of carbonic acid acid residue (SO3-).
If the solution (melt) electrolyte placed in an electrolytic cell (vessel with a cathode and anode), when a voltage is applied to start the directed movement of charged particles to the electrodes of opposite charge: positive cations - to the negatively charged cathode, while negative anions - to positivecharged anode.This property of the electrolyte, in particular, dissociation of salts commonly used in the art.By electrolysis is carried out industrial production of aluminum, copper (electrolytic refining).Electrolysis produces the purest substances such purity can not be achieved by other methods (distillation, crystallization, and others).With electrolysis metals recovered from ores, cleaned, since the cathode is deposited only on the metal cation and the impurities remain in solution or melt.The phenomenon of dissociation of salts underlies produce pure hydrogen and pure chlorine.The water dissolves the sodium chloride ions: sodium cation and chlorine anion.At the anode, pure chlorine is released at the cathode - a byproduct of hydrogen and in the solution will form another important byproduct - sodium hydroxide.
