Page 115 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1

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

as Ag CrO is an unsymmetrical salt while AgCl is a symmetrical salt which has a
2 4
different number of ions.

-10
Ksp AgCl 1.82 z× 10

Ksp Ag2CrO4 1.1 X 10
-12

+
-
Ksp AgCl= [Ag ][Cl ]
X = 1.82 × 10
-10
2
-5
X= 1.34 × 10
-2
Ksp Ag2CrO4= [2Ag ] [CrO4 ]
+ 2
-12
3
4X = 1.1 X 10
-5
X= 6.5 × 10
are salts in which the valence of the cation radicle = the valence of the
Symmetrical salts
anion radicle such as AgCl , CaSO ……. etc.
4
Non-symmetrical are salts in which the valence of the cation radicle  the valence of the

salts anion radicle) such as Ag CrO , PbI ......etc.
2
4
2

• As a general rule: When comparing the solubilities of two salts, you can sometimes
simply compare the relative values of their K , provided that they have the same
sp
number of ions!
Example:

-12 -10 -5
CuI has K = 5.0 x 10 , BaSO has K = 1.0 x 10 and CaSO has K = 6.1 x 10 .
sp 4 sp 4 sp
Example:

-12 -10 -5
CuI has K = 5.0 x 10 , BaSO has K = 1.0 x 10 and CaSO has K = 6.1 x 10 .
sp 4 sp 4 sp
• Since the K for calcium sulfate > K for Barium sulfate > K for copper (I) iodide,
sp sp sp
we can say that:
calcium sulfate > barium sulfate >copper (I) iodide in solubility

• they are all symmetrical salts having the same number of ions

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