Solubility equilibria

Question 1

Defn. saturated solution

Answer 1

a solution in which the maximum amount of solute/ salt has been dissolved

Question 2

Solubility product, Ksp

Answer 2

Equilibrium constant

Ksp = [M^(Y+) (aq)]^X [A^(X-) (aq)]^Y

conc. in saturated solution

Ksp only applies to dilute solutions with total ion concentration of less than 0.01moldm^-3

Question 3

Defn. Solubility

Answer 3

Maximum concentration of solute that can be dissolved in a given amount of a particular solvent at a specific temperature

Question 4

How to use Ksp

Answer 4

Ksp can be used to compare solubility of salts with the same formula types (eg. XY, X2Y, XY2 etc.)

Ksp cannot be used to compare solubility of salts with different formula types because Ksp values will have different units

To compare solubility of salts with different formula types, we must compare solubilities rather than Ksp

Question 5

Ionic product

Answer 5

Ionic product = [M^(Y+) (aq)]^X [A^(X-) (aq)]^Y

conc. of ions in any solution after mixing

Question 6

ionic product < Ksp

Answer 6

1. the solution is unsaturated
2. no precipitate is formed
3. More salt can be dissolved to increase [ion] further

Question 7

ionic product = Ksp

Answer 7

1. solution has reached saturation point
2. no precipitate is formed (system is in equilibrium, rate of dissolving = rate of precipitation)

Question 8

ionic product > Ksp

Answer 8

1. resulting mixture contain the maximum concentration of the ions governed by the Ksp value i.e. solution contains higher [ion] than in the saturated solution
2. precipitation occurs to lower the [ion] further

Question 9

Defn. Common Ion effect

Answer 9

refers to the lowering of the solubility of an ionic compound due to the addition of a common ion

Question 10

Effect of common ion on solubility

Answer 10

1. the presence of Fe2+ from FeSO4 increases the [Fe2+]
2. By LCP, the POE of (2) shifts to the left, decreasing the solubility of Fe(OH)2