Page 5 - Pharmaceutical analytical chemistry |

Solubility rules

a- All Li+, Na+, K+ & NH4+ salts are soluble.

b- All acetates and nitrates are soluble.

c- All chlorides, bromides and iodides are soluble

Except ⎯→ Ag+, Hg22+ and Pb2+ salts together with HgBr2 & HgI2.

d- All sulfates are soluble

Except → Ca2+, Sr2+, Ba2+& Pb2+ together with Ag2SO4 & Hg2SO4.

e- All carbonates, phosphates and sulfides are insoluble

Except ⎯→ group IA & NH4+

f- All hydroxides are insoluble

Except ⎯→ group IA & Ca (OH)2, Sr (OH)2 & Ba (OH)2

Degree of Dissociation

Molecules Cations + Anions

Arrhenius introduced a quantity “” called the degree of

dissociation which is defined as follows:

= Number of solute molecules dissociated

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Total number of solute molecules before dissociation

Equilibrium Degree of Dissociation ““
0.92
HCl H+ + Cl- 0.92
0.013
HNO3 H+ + NO3- 0.91
0.018
CH3OOH H+ + CH3OO- 0.86
0.01
NaOH Na+ + OH-

NH4OH NH4+ + OH-

NaCl Na+ + Cl-

HgCl2 Hg2+ + 2Cl-

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