Common Ion Effect

Occurs when a reactant containing a given ion is added to an equilibrium mixture that already contains that ion and the position of equilibrium shifts away from forming more of it.

The Henderson-Hasselbalch Equation

pH=pKa + log [base]

                    [acid]

The higher the Ksp.....

the greater the solubility.

What does the presence of a common ion do?

decreases the solubility of a slightly soluble ionic compound.

What do buffers contain significant amounts of?

both a weak acid and its conjugate base

OR

both a weak base and its conjugate acid

What does the weak acid in a buffer do?

It neutralizes added base

What does the conjugate base in a buffer do?

It neutralizes added acid.

What does the weak base in a buffer do?

It neutralizes added acid.

What does the conjugate acid in a buffer do?

It neutralizes added base.

pka + pkb = 14

pka + pkb = 14

When is a buffer most effective?

when the concentrations of acid and conjugate base are equal (an effective buffer must have a [base]/[acid] ratio in the range of 0.10 to 10.)

when the concentrations of acid and conjugate base are highest. (the more dilute the buffer components, the less effective the buffer.)

Buffer Range

pka plus or minus 1

Buffer Capacity

the amount of acid or base that can be added to a buffer without destroying its effectiveness

Solubility Product Constant (K_sp)

the equilibrium expression for a chemical equation representing the dissolution of an ionic compound

Molar Solubility (S)

the solubility in units of moles per liter (mol/L)

What happens to the solubility of an ionic compound in the presence of an common ion?

The solubility of an ionic compound in a solution containing a common ion than in pure water.

What does the solubility of an ionic compound with a strongly basic or weakly basic anion do?

The solubility of an ionic compound with a strongly basic or weakly basic anion increases with increasing acidity (decreasing pH).

(Common basic anions include OH^-, S^2-, and CO_3^2-)

Strong Acids

HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄

Weak Acids

HF, HCN, H₂S, HClO, HNO₂, H₃PO₄,

Organic Acids (RCOOH)

Strong Bases

M₂O or MOH (M=group 1A Metal)

MO or M(OH)₂ (M=group 2A Metal)

Weak Bases

Ammonia and Amines

Q_sp = K_sp

the solution is saturated and no change occurs

Q_sp>K_sp

Precipitate forms until solution is saturated

Q_sp < K_sp

Solution is saturated and no precipitate forms

How a buffer works

Strong Acid/ Strong Base Titration Curve

Weak Acid/ Strong Base Titration Curve

Strong Acid/ Weak Base Titration Curve

Polyprotic Acid Titration Curve