Equilibrium of Other Reactions

Solubility Constant

K_sp

Large K_sp

Solubility is high

Small K_sp

Solubility is low

Molar Solubility (Molarity)

• Used to find concentrations of ions

• K_sp

Having a 1:1 ratio of ions in solution yields?

The concentration of each individual ion and the molar solubility are equivalent.

Concentration of given ion increases:

Solubility will decrease

Concentration of given ion increases:

Solubility will increase

Q = K_sp

Solution is at equilibrium and perfectly saturated

Q > K_sp

• Supersaturated solution

• Precipitate forms

• Shifts left so solid remains

Q < K_sp

• Unsaturated solution

• No precipitate

• Shifts right so solid dissolves

What affects K?

Temperature

What is the common ion effect?

The reduction in solubility of an ionic compound when a soluble compound with a matching ion is added to the solution.

Common ion effect v. equilibrium

A common ion increases product concentration so the reaction shifts left to form solid, decreasing the compound's solubility.

Does adding a common ion change the value of K_sp

NO

Selective precipitation

Separating ions by adding a counter-ion that precipitates them one at a time based on their Ksp values.

Lewis acid

Accepts e^-

Lewis base

Donates e^-

Lower concentration of compound

Precipitate first

Higher concentration of compound

Precipitate last

K_w

1.0×10^-14