Solubility Product

Solubility Product

Solubility Product

Solubility Product (Ksp)

Solubility product is defined as- in the saturated solution, the product of concentrations of the ions raised to a power equal to the number of times, the ions occur in the equation representing the dissociation of the electrolyte at a given temperature.
Consider in general, the electrolyte of the type AxBywhich is dissociated as-
AxBy ⇌ xA+y + yB−x
Applying law of mass action-
K = [A+y]x [B−x]y/[AxBy]
or, K [AxBy] = [A+y]x [B−x]y
for saturated solution-
[AxBy] = constant
so, Ksp = [A+y]x [B−x]y

Q. The solubility of barium sulphate at 298 K is 1.05 x 10-5 mol dm-3. Calculate the solubility product.

BaSO4 ⇌ Ba+2 + SO4-2
[Ba+2] = 1.05 x 10-5 mol dm-3
[SO4-2] = 1.05 x 10-5 mol dm-3
So, Ksp = [Ba+2] [SO4-2]
or, Ksp = 1.05 x 10-5 X .05 x 10-5
or, Ksp = 1.10 x 10-10 mol2 dm-6

Q. If the solubility product of magnesium hydroxide is 2.00 X 10-11 mol3 dm-9 at 298 K, calculate its solubility in mol dm-3 at that temperature.

Answer: 1.71 X 10-4 mol dm-3