Page 33 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1

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

Different equilibrium constants
1. Ionization constant for acids or bases: (Ka or Kb)

2. Ionization constant of water: (Kw)

1. Ionization constant for acids or bases: (K or K )
a b

+
-
CH3COOH ↔ CH3COO + H
[H + ][CH COO − ]
K a = 3
[CH 3 COOH]
Q. what will happen if we add HCl to the above reaction?
Acid dissociation:
+
H2S ↔ 2H + S 2-
[H + ][HS − ]
K =
a) Acid 1. H2S ↔ H + HS - 1 [H 2 S]
+
dissociation: K = [H + ][S 2− ]
2
-
+
2. HS ↔ H + S 2- [HS − ]
[H + ] 2 [S 2− ]
K 1,2 = [H S]
+
3. H2S ↔ 2H + S 2- 2

K1 is always > K2 & K2 is always > K3 in case of polyprotic
acids.

+
-
NH4OH ↔ NH4 + OH
+
−
[OH ][NH ]
4
b) Base =

4
dissociation: [NH OH]
Q. what would happen if we added NH4Cl to the above reaction?

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