Page 125 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1 2024-2025

Mansoura National University
Pharm D-Clinical Pharmacy Program Level 1 Pharm. Anal. Chem. 1 (PC 101)

• When AgCl is placed in water, an equilibrium is established when the rate of
dissolution of ions from the solid equals the rate of precipitation of ions

from the saturated solution.
+ -
AgCl (s) Ag (aq) + Cl (aq)

• Since the concentration of pure solid is constant,

• The solubility product constant (Ksp) is:

[ ] Brackets mean molar concentration or molar solubility of ions

For salts that have more than two ions per formula unit, the ion concentrations must
be raised to the powers indicated by the coefficients of the balanced equation:
A B (s) ↔ a A (aq) + b B(aq)
a b

a b
Ksp = [A] [B]

-
2+
Mg (OH)2 (s) ↔ Mg (aq) + 2 OH (aq)
- 2
2+
Ksp = [Mg ] [OH ]
2-
3+
Bi2S3 (s) ↔ 2 Bi (aq) + 3 S (aq)
2- 3
Ksp = [Bi ] [S ]
3+ 2
Quiz

Write the solubility product constant expression (Ksp) for the following
reactions:

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