Solubility, Precipitation, and Complex Ions

Manual: General · Subject: Chemistry

Predict whether compounds dissolve, precipitate, or form coordination complexes.

Ions in water

Solubility rules

Solubility depends on lattice energy, hydration energy, and specific ion interactions. Many nitrates and alkali metal salts are soluble, while some combinations such as silver chloride are poorly soluble.

Ksp

For a sparingly soluble salt $A_xB_y$ , the solubility product constant expresses the equilibrium between the solid and its dissolved ions. Larger $K_{sp}$ values generally indicate greater solubility, though comparison is easiest for salts with the same stoichiometry.

Predicting precipitation

1

Step 1: Write the ions present after mixing.
2

Step 2: Swap partners to form possible products.
3

Step 3: Use solubility rules or $K_{sp}$ values to test each product.
4

Step 4: If an insoluble product forms, a precipitate appears.

💡

Common driver

A precipitation reaction occurs when the ion product exceeds the solubility product, so the excess solid forms until equilibrium is restored.

Which salt is generally soluble in water?

AgCl

BaSO_4

NaNO_3

PbI_2

What does $K_{sp}$ describe?

Precipitation vs complex formation

Precipitation

Forms an insoluble solid
Removes ions from solution

Complex ion formation

A metal ion binds ligands
Can increase apparent solubility

Why can adding excess ammonia sometimes dissolve a metal hydroxide precipitate?

It lowers temperature It forms a complex ion with the metal It converts the solid into gas It destroys water molecules

Neuroanatomy Explorer

Memory Deck

Match the Pairs

Concept Constellation

Solubility, Precipitation, and Complex Ions

Ions in water

Solubility rules

Ksp

Predicting precipitation

Precipitation vs complex formation