Advanced Topic 485 of 1102 Kinetics & Equilibrium
Effect of Complexation on Solubility
Complex formation can dissolve otherwise insoluble salts, as AgCl dissolves in ammonia.
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In-depth explanation of Effect of Complexation on Solubility
Complex formation can greatly increase the solubility of a sparingly soluble salt, because the ligand removes free metal ions from solution and shifts the dissolution equilibrium forward. This follows from Le Chatelier's principle: as the free metal concentration falls, more of the solid dissolves to restore the balance. The extent of the effect depends on the magnitude of the formation constant of the complex and on the concentration of the ligand. Amphoteric metal hydroxides dissolve in excess strong base for a similar reason, since the hydroxide forms a soluble complex ion. This principle is used in qualitative analysis to separate and identify metal ions.
Going deeper: Effect of Complexation on Solubility
Key ideas: Combine equilibria: for AgCl + 2NH3 <-> Ag(NH3)2+ + Cl-, K = Ksp x Kf = 1.8 x 10^-10 x 1.7 x 10^7 = 3.1 x 10^-3. Then solve with an ICE table for the dissolved silver. This shows that the multiplication rule for K values gives the overall constant. Adding excess ligand can dissolve more solid, but too much halide can also form soluble complexes.
Common mistakes and connections: Students forget to add the complex to total dissolved metal, or treat Ksp as changed by the ligand. Ksp stays the same, and the extra solubility arises from lowered free ion concentration. Another error is assuming that every precipitate dissolves in ammonia; AgBr dissolves poorly and AgI not at all, because Ksp is too small. Connects to amphoterism and manipulating K.
Visualization of Effect of Complexation on Solubility
As ammonia forms Ag(NH3)2+ the dissolved silver rises from 1.3e-5 M in water to over 0.05 M in 3 M NH3, so AgCl dissolves. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Silver chloride dissolves in aqueous ammonia because the Ag+ ions are converted into the soluble complex Ag(NH3)2+.
Frequently asked questions about Effect of Complexation on Solubility
What is Effect of Complexation on Solubility?
Complex formation can dissolve otherwise insoluble salts, as AgCl dissolves in ammonia.
Is Effect of Complexation on Solubility a beginner, intermediate or advanced topic?
Effect of Complexation on Solubility is a advanced topic in Kinetics & Equilibrium. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Effect of Complexation on Solubility?
Study these earlier topics in Kinetics & Equilibrium first: Precipitation Prediction, Selective Precipitation, Complex Ion Equilibria.
What comes after Effect of Complexation on Solubility?
The next topics in Kinetics & Equilibrium are Equilibrium in Gas Phase and Degree of Dissociation.
Can I practise Effect of Complexation on Solubility with quizzes?
Yes. The interactive lesson includes a self-check question on Effect of Complexation on Solubility, and the Kinetics & Equilibrium quiz draws on every topic in this area.
Where Effect of Complexation on Solubility fits in Kinetics & Equilibrium
Effect of Complexation on Solubility is topic 66 of 91 in Kinetics & Equilibrium.