Chemists love to manipulate things. Ksp expressions are equilibrium expressions and as Le Chatlier showed us, equilibria can be manipulated if you apply a stress. There are many factors that influence solubility and the factors we will investigate in this class are: Common Ion, pH, Complex Ion Formation, and Amphoterism. In all of these effects, it is very important to WRITE OUT THE EQUILIBRIUM EXPRESSION so you can properly analyze how the solubility will be influenced.
The Common Ion effect is simply a direct application of Le Chatlier’s principle.
17.5 Common Ion Effect
The pH of a solution has a dramatic influence of the solubility. When investigating pH effects, it is important for you to know the strong acids, which will allow you to identify all the neutral anions in solution.
17.5 pH Effects
17.5 How does adding acid/base influence solubility?
Le Chatlier’s principle does a great job of explaining the solubility in terms of the common ion effect and pH effects, but in some instances some puzzling results are obtained. For instance, when concentrated NH3 is added to a saturated solution of Zn(OH)2 its solubility increases. Now we need to determine why this is, and if Le Chatlier’s principle is still valid.
17.5 Does zinc hydroxide follow the rules we’ve discussed so far?
It turns out Le Chatlier’s principle still applies, but there is something else going on in solution responsible for these results. The concept responsible for the difference in solubility is complex ion formation.
17.5 Complex ion formation and coordination complexes
This allows us to investigate zinc hydroxide in a more complex way and it allows us to perform several calculations based on complex ion formation.
17.5 Re-analyzing zinc hydroxide
17.5 Solubility of zinc hydroxide in 15 M NH3
17.5 Determining the concentration of free metal cations in solution
Amphoterism is a special case where a slightly soluble salt has its solubility increased due to pH effects in acidic solution and has its solubility increased due to complex ion formation under basic conditions.
17.5 Solubility of Al(OH)3 in 15 M NH3
17.5 Molar Solubility of Al(OH)3 in 15 M NH3 continued
17.5 Amphoteric Effects on Solubility