SOLUBILITY PRODUCT
This presentation delves into the concept of sparingly soluble salts and their solubility products (Ksp). It defines sparingly soluble salts, explaining how they dissolve to a limited extent and illustrates the equilibrium established in saturated solutions. The solubility product is introduced as a new constant (Ks.p) derived from the ionic concentrations of a salt at equilibrium. Limitations of Ksp, including effects of temperature and the common ion effect, are examined, providing insight into how the solubility of a salt is influenced by the presence of other ions in solution.
SOLUBILITY PRODUCT
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SOLUBILITYPRODUCT Presentation on
Insoluble salts are describe as sparingly soluble. A sparingly soluble salts dissolves to a small extent. The solubility product is the new constant formed when the constant (Kc) multiplied by the concentration of the salt at a given temperature.
Let AxBy represent a sparingly soluble salt At equilibrium; For a saturated solution of ionic solid in water: AxBy(s) xAy+(aq) + yBx-(aq)
The new constant form from the product of constants Kc and AxBy(s) is Ks.p.. • Ks.p. represents the solubility product of the sparingly soluble salt AxBy(s).
Example A Saturated solution of silver chloride contains 1.46 10-3 gdm-3 at 18°C. What is the solubility product of silver chloride at this temperature?
Ksp is valid only for saturated solution in which the total concentration of the ions is no more than 0.01 mol dm-3. • Ksp is affected by temperature since it is an equilibrium constant.
In the presence of either Ay+ or Bx- from a second source, the solubility of the salt AxBy is reduced known as Le Chatalier’s principle. • The common ion effect is the precipitation of a solute on addition of another solution which has an ion in common with the solute.
Example • There is disruption in the equilibrium system but the(Ksp) would remain constant upon the addition of sodium sulphate to saturated solution of BaSO4(s). • BaSO4(s) Ba2+(aq) + SO2-4(aq) • NaSO4(s) 2Na+(aq) + SO2-4(aq)
There would be an increase in the SO2-4 ions concentration due to the addition of NaSO4(s) to the BaSO4(s). • The Ksp would remain constant due to the increase of SO2-4 ions consequenting in a decrease in Ba2+(aq) ions concentration. • Thus the equilibrium would shift and the reduction of BaSO4 would occur.
Ionic product < Ks.p, , no precipitation occurs. • Ionic product = Ks.p. , a saturated solution forms. • Ionic product > Ks.p. , precipitation occurs.
Hence Kc = [Ay+(aq)]x [Bx-(aq)]y [AxBy(s)] [Kc][AxBy(s)] = [Ay+(aq)]x [Bx-(aq)]y Ks.p. = [Ay+(aq)]x [Bx-(aq)]y
The solubility of silver chloride at 18°C = 1.46 10-3 g dm-3 = 1.46 10-3 143.5 mol dm -3 = 1 10 -5 mol dm -3
