Equilibria Involving Complexes

The sum of the two terms on the right-hand side of this equation is zero, so we can equate them. After dividing by K[B]m 1, we obtain 

By expanding the left-hand side and letting C = [A] + [B], we find that 

This result signifies that the maximum in the amount of complex formed from a fixed total concentration of A plus B will occur when A and B are present in the solution in precisely the same ratio as they are in the complex. 

This procedure has been used successfully to determine the composition of many complexes in solution. It is possible to extend this method to cases where more than one complex is formed but the application is quite difficult. Like the logarithmic method, Job s method can be applied to other cases of molecular interaction and is not limited to the formation of coordination compounds. Both methods are based on the assumption that one complex is dominant in the equilibrium mixture. Numerous other methods for determining the number of metal ions and ligands in complexes have been devised, but they are beyond the introduction to the topic presented here. 

In the preceding section, we have described two methods that are frequently used to determine the composition of complexes in solution. We will now turn our attention to a consideration of the simultaneous equilibria that are involved in complex formation. The widely used approach described here is known as Bjerrum s method, and it was described by Jannik Bjerrum many years ago. 

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Although this treatment of buffers was based on acid-base chemistry, the idea of a buffer is general and can be extended to equilibria involving complexation or redox reactions. For example, the Nernst equation for a solution containing Fe + and Fe + is similar in form to the Henderson-Hasselbalch equation. 

In Section 16-6, we describe how metal cations in aqueous solution can form bonds to anions or neutral molecules that have lone pairs of electrons. This leads to formation of complex ions and to chemical equilibria involving complexation. The complexation equilibrium between Ag and NH3 is an example ... 

Strongly influences positions of equilibria involving complex ions and metal-chelate formation. 

Hunt, J. P., Metal Ions in Aqueous Solution, Benjamin, 1963 (structures of water and ionic solutions, equilibria involving complex ions, rates and mechanisms and redox reactions). 

Equilibria Involving Complex Ions Formattan of Complex fons Complex bns and Solubilty... 

The equilibria involving complex ions and precipitates have applications in geology, medicine, and agriculture. In chemistry, you are more likely to meet up with these equilibria in the laboratory when you carry out experiments in qualitative analysis. 

Criteria for Precipitation and Its Completeness 18-6 Fractional Precipitation 18-7 Solubility and pH 18-8 Equilibria Involving Complex Ions 18-9 Qualitative Cation Analysis... 

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