DISSOCIATION CONSTANTS OF INORGANIC ACIDS AND BASES
The data in this table are presented as values of pKa, defined as
the negative logarithm of the acid dissociation constant Ka for the
reaction
can be calculated from the equation
OH−   NH 4 + 


K b = K water /K a = 
[ NH 3 ]
BH  B– + H+
Thus pKa = –log Ka , and the hydrogen ion concentration [H+] can
be calculated from
H+  B− 
Ka =    
[ BH ]
In the case of bases, the entry in the table is for the conjugate acid;
e.g., ammonium ion for ammonia. The OH– concentration in the
system
where Kwater = 1.01 × 10–14 at 25 °C. Note that pKa + pKb = pKwater.
All values refer to dilute aqueous solutions at zero ionic strength
at the temperature indicated. The table is arranged alphabetically
by compound name.
Reference
1. Perrin, D. D., Ionization Constants of Inorganic Acids and Bases in
Aqueous Solution, Second Edition, Pergamon, Oxford, 1982.
NH3 + H2O  NH4+ + OH–
Name
Aluminum(III) ion
Ammonia
Arsenic acid
Formula
Al+3
NH3
H3AsO4
Arsenious acid
Barium(II) ion
Boric acid
H2AsO3
Ba+2
H3BO3
Calcium(II) ion
Carbonic acid
Ca+2
H2CO3
Chlorous acid
Chromic acid
HClO2
H2CrO4
Cyanic acid
Germanic acid
HCNO
H2GeO3
Hydrazine
Hydrazoic acid
Hydrocyanic acid
Hydrofluoric acid
Hydrogen peroxide
Hydrogen selenide
N2H4
HN3
HCN
HF
H2O2
H2Se
Hydrogen sulfide
H2S
Hydrogen telluride
H2Te
Hydroxylamine
Hypobromous acid
Hypochlorous acid
Hypoiodous acid
Iodic acid
Lithium ion
Magnesium(II) ion
Nitrous acid
Perchloric acid
Periodic acid
Phosphoric acid
NH2OH
HBrO
HClO
HIO
HIO3
Li+
Mg+2
HNO2
HClO4
HIO4
H3PO4
Step
1
2
3
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
t/°C
25
25
25
25
25
25
25
20
20
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
18
25
25
25
25
25
25
25
25
25
20
25
25
pKa
5.0
9.25
2.26
6.76
11.29
9.29
13.4
9.27
>14
12.6
6.35
10.33
1.94
0.74
6.49
3.46
9.01
12.3
8.1
4.6
9.21
3.20
11.62
3.89
11.0
7.05
19
2.6
11
5.94
8.55
7.40
10.5
0.78
13.8
11.4
3.25
-1.6
1.64
2.16
8-40
Section 8.indb 40
4/30/05 8:46:44 AM
Dissociation Constants of Inorganic Acids and Bases
Name
Section 8.indb 41
Formula
Phosphorous acid
H3PO3
Pyrophosphoric acid
H4P2O7
Selenic acid
Selenious acid
H2SeO4
H2SeO3
Silicic acid
H4SiO4
Sodium ion
Strontium(II) ion
Sulfamic acid
Sulfuric acid
Sulfurous acid
Na+
Sr+2
NH2SO3H
H2SO4
H2SO3
Telluric acid
H2TeO4
Tellurous acid
H2TeO3
Tetrafluoroboric acid
Thiocyanic acid
Water
HBF4
HSCN
H2O
8-41
Step
2
3
1
2
1
2
3
4
2
1
2
1
2
3
4
2
1
2
1
2
1
2
t/°C
25
25
20
20
25
25
25
25
25
25
25
30
30
30
30
25
25
25
25
25
25
18
18
25
25
25
25
25
pKa
7.21
12.32
1.3
6.70
0.91
2.10
6.70
9.32
1.7
2.62
8.32
9.9
11.8
12
12
14.8
13.2
1.05
1.99
1.85
7.2
7.68
11.0
6.27
8.43
0.5
–1.8
13.995
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