Utterly Confused About Complex Ions

In order to do a problem involving the formation of a complex ion requires you to know the value of x. While x is usually either 4 or 6, it can have other values. How can you tell what x is You must have additional information. Your instructor or textbook may tell you directly what x will be. In other cases, you may need to examine a table of formation constants, Kf. If you see, for example, Kf for [Fe(C204)3]3 4 5 is equal to some value, the subscript 3 tells you that x = 3. 

To change the general equation to a specific equation entails a simple substitution of the formulas. Using [Fe(C204)3]3 as an example, we see that M = Fe3+ and L = C204, to give the equation  

This leads to the following equilibrium constant expression  

A Make sure you move the ion charges inside the bracket so they are not mistaken for exponents. 

Once you have the correct equilibrium constant expression, there is no difference in solving the complex ion equilibrium than any other equilibrium problem. 

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