Page 113 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1

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

-5
2+
[Ba ] = 1.05 x 10 mol dm
-3
-3
2-
-5
[SO4 ] = 1.05 x 10 mol dm
2+
Ksp = [Ba ] [SO4 ] = 1.10 x 10 mol dm
-10
2
2-
-6
Significance of Ksp

1) For a precipitate of AgCl (for example) to be formed in a solution:
+ -
• The precipitate will be formed only when the ionic product (Q) of [Ag ] and [Cl ]
exceeds the Ksp.
+ -
• If the product just equals Ksp all Ag and Cl will remain in solution.
+ -
• [Ag ][Cl ] (ionic product, Q) must be > Ksp of AgCl.

2) For comparing the solubilities of different sparingly soluble salts:

 Solubility product (K ) ≡  Solubility ……… & vice versa.
sp
• (This works if the compared salts have the same number of ions!)

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