Encyclopedia of Environmental Science and Engineering, Volume I and II

1264 WATER CHEMISTRY

TABLE 3 (continued )

Reaction

Symbol for

equilibrium

constants log K (25C) I

9.0 5 C, 200 atm

seawater

CaCO 3 (calcite)  Ca^2   CO 32  Ks0 8.35 0

6.2 Seawater

CaCO 3 (aragonite)  Ca^2   CO 32  Ks0 8.22 0

SrCO 3 (s)  Sr^2 CO 22  Ks0 9.03 0

6.8 Seawater

ZnCO 3 (s)  2H  Zn^2   H 2 O  CO 2 (g) *Kps0 7.95 0

Zn(OH)1.2(CO 3 )0.4(s)  2H  Zn^2   H 2 O 

CO 2 (g)

*K 0 9.8 0

Cu(OH)(CO 3 )0.5(s)  2H  Cu^2   3/2H 2 O 

1/2CO 2 (g)

*Kps0 7.08 0

Cu(OH)0.67(CO 3 )0.67(s)  2H  Cu^2  

4/3H 2 O  2/3CO 2 (g)

*Kps 7.08 0

MgCO 3 (magnesite)  Mg^2   CO 32  Ks0 4.9 0

MgCO 3 (nesquehonite)  Mg^2   CO 32  Ks0 5.4 0

Mg 4 (CO 3 ) 3 (OH) 2 .3H 2 O(hydromagnesite)  4Mg^2  

3CO 32  2OH

Ks0 29.5 0

CaMg(CO 3 ) 2 (dolomite)  Ca^3   Mg^2   2CO 32  Ks0 16.7 0

FeCO 3 (siderite)  Fe^2   2CO 32  Ks0 10.4 (10.24) 0

CdCO 3 (s)  2H  CD^2   H 2 O  CO 2 (g) Kps0 6.44 1M NaCl 4

MnCO 3 (s)  Mn^2 2CO 32  Ks0 10.41 0

III. SULFATES, SULFIDES, AND SILICATES

CaSO 4 (s)  Ca^2   SO 42  Ks0 4.6 0

H 2 S  H  HS K 1 7.0 0

HS  H  S^2  K 2 12.96 0

MnS(green)  Mn^2   S^2  Ks0 12.6 0

MnS(pink)  Mn^2   S^2  Ks0 9.6 0

FeS(s)  Fe^2   S^2  Ks0 17.3 0

SiO 2 (quartz)  2H 2  H 4 SiO 4 Ks0 3.7

(am)SiO 2 (s)  2H 2 O  H 4 SiO 4 Ks0 2.7 0

H 4 SiO 4  H  H 3 SiO 4 Ks0 9.46 0

IV. ACIDS

NH 4  N  NH 3 (aq) Ka 9.3 0

HOCl  H  OCl Ka 7.53 0

The constants given here are taken from quotations or selections in (a) L. G. Sillén and A. E. Martell, Stability

Constants of Metal Ion Complexes, Special Publ., No. 17, the Chemical Society, London, 1964: (b) W. Feitknecht

and P. Schindler, Solubility Constants of Metal Oxides, Metal Hydroxides and Metal Hydroxide Salts in Aqueous

Solutions, Butterworths, London, 1963; (c) P. Schindler, “Heterogeneous Equilibria Involving Oxides, Hydroxides,

Carbonates and Hydroxide Carbonates”, in Equilibrium Concepts in Natural Water Systems, Advance in Chemistry

Series, No. 67, American Chemical Society, Washington, DC, 1967, p. 196; and (d) J. N. Butler, Ionic Equilibrium,

A Mathematical Approach, Addison-Wesley Publishing, Reading, Mass., 1964. Unless otherwise specified a pressure

of 1 atm is assumed.

a Most of the symbols used for the equilibrium constants are those given in Stability Constants of Metal-Ion Complexes

Table from Stumm, W. and J. Morgan, Aquatic Chemistry, Wiley-Interscience, New York, 1970, pp. 168 and 169.

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