Buffer Solutions, pH Calculations, and Solubility Equilibria in Chemistry

What do buffers contain?

Significant amounts of both a weak acid and its conjugate base (or a weak base and its conjugate acid).

What happens when a small amount of acid is added to a buffer?

It converts a stoichiometric amount of base to the conjugate acid.

What happens when a small amount of base is added to a buffer?

It converts a stoichiometric amount of the acid to the conjugate base.

What is the optimal condition for a buffer to work effectively?

The amounts of acid and conjugate base should be large and approximately equal.

What occurs if the relative amounts of acid and base in a buffer differ by more than a factor of 10?

The ability of the buffer to neutralize added acid and base diminishes.

What is the maximum pH range at which a buffer is effective?

One pH unit on either side of the acid's pKa.

What is a titration curve?

A graph of the change in pH versus added volume of acid or base during a titration.

What types of acid-base reactions are represented by titration curves?

Strong acid with strong base, weak acid with strong base, and polyprotic acid with strong base.

What is the equivalence point in a titration?

The point at which the amount of acid equals the amount of base, often indicated by a color change from an indicator.

What is the solubility product constant (Ksp)?

An equilibrium constant for the dissolution of an ionic compound in water.

How can molar solubility of an ionic compound be determined?

From Ksp and vice versa.

What is selective precipitation?

A method where an added reagent forms a precipitate with one dissolved cation but not others.

What is the principle of qualitative chemical analysis?

A mixture of cations can be separated and analyzed based on the differences in the solubilities of their salts.

What is a complex ion?

A central metal ion coordinated to two or more ligands.

What is a formation constant?

The equilibrium constant for the formation of a complex ion, usually quite large.

How does the presence of Lewis bases affect the solubility of ionic compounds?

It increases the solubility because the formation of the complex ion drives the dissolution reaction to the right.

What happens to the solubility of metal hydroxides in the presence of acids?

All metal hydroxides become more soluble.

What additional effect do amphoteric metal hydroxides have in the presence of bases?

They also become more soluble.

What does it mean if Q < Ksp?

The solution is unsaturated, and more of the solid ionic compound can dissolve.

What does it mean if Q = Ksp?

The solution is saturated, holding the maximum amount of dissolved ionic compound.