Appendix

Ionization Constants for Select Acids

Ka determined at 25 °C.

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Acid

Formula and Ionization Equation

Ka

pKa

Acetic

CH3COOH + H2O ⇌ H3O+ + CH3COO

1.8 × 105

4.74

Arsenic

H3AsO4 + H2O ⇌ H3O+ + H2AsO4

K1 = 6.17 × 103

2.210

H2AsO4 + H2O ⇌ H3O+ + HAsO42

K2 = 1.17 × 107

6.932

HAsO42 + H2O ⇌ H3O+ + AsO43

K3 = 3.09 × 1012

11.523

Benzoic

C6H5COOH + H2O ⇌ H3O+ + C6H5COO

1.2 × 104

3.92

Boric

B(OH)3(H2O) + H2O ⇌ H3O+ + B(OH)4

5.8 × 1010

9.24

Carbonic

H2CO3 + H2O ⇌ H3O+ + HCO3

K1 = 4.3 × 107

6.37

HCO3+ H2O ⇌ H3O+ + CO32

K2 = 4.7 × 1011

10.33

Citric

H3C6H5O7 + H2O ⇌ H3O+ + H2C6H5O7

K1 = 1.4 × 103

2.85

H2C6H5O7 + H2O ⇌ H3O+ + HC6H5O72

K2 = 4.5 × 105

4.35

HC6H5O72 + H2O ⇌ H3O+ + C6H5O73

K3 = 1.5 × 106

5.82

Chlorous

HClO2 + H2O ⇌ H3O+ + ClO2

1.1 × 102

1.96

Formic

HCOOH + H2O ⇌ H3O+ + HCOO

3.0 × 104

3.52

Hydrazoic

HN3 + H2O ⇌ H3O+ + N3

1.0 × 105

5.00

Hydrocyanic

HCN + H2O ⇌ H3O+ + CN

3.3 × 1010

9.48

Hydrofluoric

HF + H2O ⇌ H3O+ + F

6.8 × 104

3.17

Hydrogen peroxide

H2O2 + H2O ⇌ H3O+ + HO2

2.1 × 1012

11.68

Hydrosulfuric

H2S + H2O ⇌ H3O+ + HS

K1 = 1 × 107

7.0

HS + H2O ⇌ H3O+ + S2

K2 = 1 × 1019

19.0

Hypochlorous

HOCl + H2O ⇌ H3O+ + OCl

6.8 × 108

7.17

Nitrous

HNO2 + H2O ⇌ H3O+ + NO2

7.41 × 104

3.130

Oxalic

H2C2O4 + H2O ⇌ H3O+ + HC2O4

K1 = 5.5 × 102

1.26

HC2O4 + H2O ⇌ H3O+ + C2O42

K2 = 1.4 × 104

3.85

Phenol

HC6H5O + H2O ⇌ H3O+ + C6H5O

1.7 × 1010

9.77

Phosphoric

H3PO4 + H2O ⇌ H3O+ + H2PO4

K1 = 7.2 × 103

2.14

H2PO4 + H2O ⇌ H3O+ + HPO42

K2 = 6.3 × 108

7.20

HPO42 + H2O ⇌ H3O+ + PO43

K3 = 4.6 × 1013

12.34

Phosphorous

H3PO3 + H2O ⇌ H3O+ + H2PO3

K1 = 2.4 × 102

1.62

H2PO3 + H2O ⇌ H3O+ + HPO32

K2 = 2.9 × 107

6.54

Propanoic

CH3CH2COOH + H2O ⇌ H3O+ + CH3CH2COO

1.33 × 105

4.85

Selenic

H2SeO4 + H2O ⇌ H3O+ + HSeO4

K1 = very large

---

HSeO4 + H2O ⇌ H3O+ + SeO42

K2 = 2.2 × 102

1.66

Selenous

H2SeO3 + H2O ⇌ H3O+ + HSeO3

K1 = 2.5 × 103

2.60

HSeO3 + H2O ⇌ H3O+ + SeO32

K2 = 1.6 × 109

8.80

Sulfuric

H2SO4 + H2O ⇌ H3O+ + HSO4

K1 = very large

---

HSO4 + H2O ⇌ H3O+ + SO42

K2 = 1.1 × 102

1.96

Sulfurous

H2SO3 + H2O ⇌ H3O+ + HSO3

K1 = 1.7 × 102

1.77

HSO3 + H2O ⇌ H3O+ + SO32

K2 = 6.3 × 108

7.2

Tellurous

H2TeO3 + H2O ⇌ H3O+ + HTeO3

K1 = 7.1 × 107

6.15

HTeO3 + H2O ⇌ H3O+ + TeO32

K2 = 4.0 × 109

8.40
Taken from Hogfeldt, E. and Perrin, D. D., Stability Constants of Metal-Ion complexes, 1st ed. Oxford: New York: Pergamon, 1979-1982. International Union of Pure and Applied Chemistry Commission on Equilibrium Data.
From Myers, R., Journal of Chemical Education, Vol. 63, 1986, pp. 687-690.

 

Ionization Constants for Select Bases

Kb determined at 25 °C.


Base Formula and Ionization Equation Kb pKb

Ammonia

NH3 + H2O ⇌ NH4+ + OH

1.77 × 105

4.752

Aniline§

C6H5NH2 + H2O ⇌ C6H5NH3+ + OH

3.9 × 1010

9.41

Dimethylamine§

(CH3)2NH + H2O ⇌ (CH3)2NH2+ + OH

5.8 × 104

3.24

Ethylenediamine

(CH2)2(NH2)2 + H2O ⇌ (CH2)2(NH2)2H+ + OH

K1 = 7.8 × 105

4.11

(CH2)2(NH2)2H+ + H2O ⇌ (CH2)2(NH2)2H22+ + OH

K2 = 2.1 × 108

7.68

Hydrazine

N2H4 + H2O ⇌ N2H5+ + OH

K1 = 1.2 × 106

5.92

N2H5+ + H2O ⇌ N2H62+ + OH

K2 = 1.3 × 1015

14.89

Hydroxylamine

NH2OH + H2O ⇌ NH3OH+ + OH

9.3 × 109

8.03

Methylamine

CH3NH2 + H2O ⇌ CH3NH3+ + OH

5.0 × 104

3.30

Pyridine

C5H5N + H2O ⇌ C5H5NH+ + OH

1.6 × 109

8.80

Trimethylamine§

(CH3)3N + H2O ⇌ (CH3)3NH+ + OH

6.2 × 105

4.21
Taken from Hogfeldt, E. and Perrin, D. D., Stability Constants of Metal-Ion complexes, 1st ed. Oxford: New York: Pergamon, 1979-1982. International Union of Pure and Applied Chemistry Commission on Equilibrium Data.
From Read, A. J., Journal of Solution Chemistry, Vol. 11, No. 9, 1982, pp. 649-664.
§From Meites, L., Ed. Handbook of Analytical Chemistry, 1st ed. New York: McGraw-Hill, 1963.

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