The stability of the fit.
Last Update: 2020-10-29
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stability of the third section of the ligand
I, dissoluted balance with ions
this reaction is called a mate reaction (also known as a lying reaction).
because the ions are combined by the central ion and the mating body with the price bond, they are relatively stable in the aqueous solution. But it is not completely unable to disintegration into simple ions, in essence and weak electrolytes similar, there is a weak phenomenon of dissoluation.
. (i) The stability of the stability constant
mate of the mate can be expressed by the equilibrium constant of the resulting mate, for example:
applies the principle of chemical balance, the greater the
K stable value, indicating that the greater the tendency to form the ion matching, the more stable the mate. Therefore, the generation constant of ions is also called a stable constant (Appendix VIII).
(ii) distribution stability constant
the production and dissocation of the mate in the solution, similar to polyacinolic acids and alkalis, is also graded, and the dissocation or generation of constants at all levels is not the same. For example, the step-by-step stabilization constants (30 degrees C) in the step-by-step coordination process between Cu2 plus and NH3 are:
K1, K2, K3, K4 is called a step-by-step stabilization constant. As can be seen from above, the step-by-step stable constant of the mate decreases with the increase of the number of numbers. It is generally believed that with the increase of the number of mating bodies, the repulsion between the mating bodies increases, so its stability decreases.
the following relationship between the step-by-step stability constant and the stability constant of the
K-K1, K2-K3-K4... Kh
Stability k is:
K, K1, K2, K3, K4×
, K4, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K, K 104) (3.17×103) (7.76×102) (1.39×102×)
1012 (iii) unstable constant
In aqueous solutions, the ag (NH.3)2) is stable, but like other weak electrolytes there are a few . . . Ag (NH.2) 3) The dissocation occurs, can be represented by the following type:
is the equilibrium constant expression is:
K instability value is longer, indicating that the more dissocation of the matching ions, so K instability is called the unstable constant of the matching ions.
. K stability and K instability are mutually inverted:
2, with the balance of the movement
metal ion Mn plus and liant A-generation ion matching MA (n-x) x, in the aqueous solution there is the following balance:
according to the principle of equilibrium movement, change the concentration of Mn plus or A-, will cause the above balance to move. If you add some kind of
to the above solution to make Mn-plus produce insoluble
, or change the oxidation state of Mn-plus, the balance will move to the left. If the acidity of the solution is changed to make A-generation of weak acids that are difficult to dissointate, the balance can also be moved to the left.
balance is also a relative equilibrium state, which is closely related to the pH value, precipitation reaction, redox reaction, etc. of the solution.
(i) relationship with acidity
proton theory, all liants can be considered an alkali. Therefore, in increasing the concentration of H-plus in the solution, because the liant and H-plus bind to a weak acid surface so that the balance of the mate moves to the right, the balance of the matching ions is destroyed, this phenomenon is called acid effect, for example:
liants are more alkaline, the less PH of the solution, the more easily the ions are destroyed.
metal ions in water, there will be different degrees of hydrolysing. The greater the PH value of the solution, the more conducive to hydrolysing. For example: Fe3 plus is prone to hydrolytic reaction in alkaline media, the more alkaline the solution, the more thorough the hydrolyzing (generating Fe(OH)3 precipitation).
as a result, in alkaline media, the balance moves to the right due to the insoluble Fe(OH) 3 precipitation of Fe3 plus water, and thus the damage is caused by the 3-3-destruction, a phenomenon known as the hydrolytic effect of metal ions.
(ii) relationship between precipitation
when ammonia is added to a solution containing silver chloride precipitation, precipitation dissolves.
. When a sodium bromide solution is added to the above solution, a pale yellow precipitation is generated.
. Since AgBr's solubility is much smaller than AgCL's, Br-Plus's ability to compete for Ag-plus is larger than CL-'s, so AgBr precipitation can be produced between AgBr and AgCL precipitation. The smaller the solubility of precipitation between sediment and metal ion generation precipitation, the more it can destroy the ions and generate precipitation.
(iii) the relationship between the redox reaction and
the occurrence of a cooperative reaction can change the oxidation capacity of metal ions. For example, when PbO2 (Pt plus) reacts with hydrochloric acid, the product is not PbCL4, but PbCL2 and CL2. But when it forms a 2-ion matching state, Pb is able to maintain its oxidation state.
with the reaction affects the direction of the redox reaction. For example, Fe3 Plus can oxidize I-Oxidize into I2:
After adding F-, the concentration of Fe3 Plus is reduced due to the generation of the F-, so that the balance moves to the left.
when we examine the effect of the matching reaction on the redox reaction, we should pay attention not only to the formation of the ion matching, but also to the stability of the ion matching.
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