Complex Ions¶

Complex ions contain a central metal cation bonded to one r more molecules or ions, called ligands

Formation¶

If the metal is in solution, it can form a complex solution through two reactions

1. Dissociation $$\hskip{1cm}\ce{Zn(NO3)2_{(s)} - >Zn_{(aq)}^{2+} + 2NO3−_{(aq)}}$$
2. Forming a complex $$\hskip{1cm}\ce{Zn_{(aq)}^{2+} + 4H2O -> Zn(H2O)4^{2+}_{(aq)}}$$

Equilibria¶

An equilibrium equation can be written for the formation of the complex, known as $$K_f$$ A large $$K_f$$ corresponds to a stable complex

$$\hskip{1cm}\ce{Co_{(aq)}^{2+} + 4Cl_{(aq)}− <-> CoCl4^{2−}_{(aq)}}$$

$$\hskip{1cm}\ce{K_f=\frac{[CoCl4^{2−}]}{[Co^{2+}][cl− ]^4}}$$

Causing Precipitation¶

If a complex reaches a neutral charge, a precipitate will form