In the broadest sense, the category of "dissociation", used in the physical and chemical terminology, defines the character of the decomposition of complex compounds on the elements that make up these compounds.Emphasizes electrolytic dissociation, which is understood as the process of disintegration of complex compounds into ions, under the influence of solvent molecules.And further, enough independent in its properties, the type of dissociation is the dissociation complex compounds.
feature of this process is due to the fact that the scope of the complex compounds are extremely different from each other in the degree of stability of the elements.It is meant, first of all, different external and internal spheres of matter.Its particles are arranged in the external area, with a very weakly bound complex ion because their connection is provided only by means of electrostatic forces.As a result - they are quite easy to detach from the base material in an aqueous solution.
This dissociation of the complex compounds called primary.It is distinguished by some features.Chief among them appears that it flows in the outer sphere and ends almost completely, and it is similar to the process that is the electrolytic dissociation of the complex compounds.There is also a version of its course.For instance, if we observe a reversible process in which the decomposition of the inner sphere, the process is called secondary dissociation of the complex compounds.
characteristic feature of the secondary dissociation is that between the complex elements of matter, ligands and the central ion equilibrium develops.An example would be such a reaction.Take the solution containing a complex ion [Ag (NH3) 2] +.If it drops to affect any chloride, the expected precipitation we did not find.The fact is that, generally, by reacting the chloride with conventional silver compounds precipitate appears in the form of silver chloride.It becomes clear that in this case, the number of ions contained in the ammonia solution is too low.It is such that, even when incorporated in a solution of excess chloride ions, does not achieve the level of solubility of silver.If, however, then the resulting solution was added potassium ions, then we get the precipitate of silver iodide.This fact shows that the silver ions, albeit in small amounts, but still present in the solution.Precipitates, the presence of which indicates that the concentration of the solution is sufficient to form a precipitate.This situation is explained by the fact that the level of solubility of silver iodide are much smaller than those of silver chloride.
According to this example, it can be concluded that the dissociation of complexes in solutions based on the laws of mass action of electronic components and therefore can be described as a kind of equilibrium constant that reflects the degree of instability of the ion.These constants are very different for different ion complexes.The reason for such a variety because the constant expressions include concentrated ions and molecules.The degree of concentration can be very different.So they determine the diversity of the instability constants of the ions.
for such phenomena as the dissociation of the complex compounds, peculiar pattern is the fact that the lower the level of concentration obtained in the reactions of the decay products, the more stable stands very complex compound, and therefore the value of the instability of the ions willbelow.The particles, which are solutions exhibit higher stability, have lower values of constant instability.
Typically, real solutions have the so-called speed dissociation of the complex, because the ratio of complexes in solution varies.In this case, the total instability constant is calculated by multiplying the values of the constants of the complexes present in a given solution.