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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 Thus pKa = –log Ka , and the hydrogen ion concentration [H+] can be calculated from 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 REFERENCE
1. Perrin, D. D., Ionization Constants of Inorganic Acids and Bases in Aqueous Solution, Second Edition, Pergamon, Oxford, 1982.
t/°C
pKa
DISSOCIATION CONSTANTS OF INORGANIC ACIDS AND BASES (continued)
t/°C
pKa
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES
This table lists the dissociation (ionization) constants of over 1070 organic acids, bases, and amphoteric compounds. All data apply to dilute aqueous solutions and are presented as values of pKa, which is defined as the negative of the logarithm of the equilibrium constant Ka for the reaction where [H+], etc. represent the concentrations of the respective species in mol/L. It follows that pKa = pH + log[HA] - log[A-], so that a solution with50% dissociation has pH equal to the pKa of the acid.
Data for bases are presented as pKa values for the conjugate acid, i.e., for the reaction In older literature, an ionization constant Kb was used for the reaction B + H2O 1 BH+ + OH- . This is related to Ka by pKa + pKb = pKwater = 14.00 (at 25°C) Compounds are listed by molecular formula in Hill order.
REFERENCES
1. Perrin, D.D., Dissociation Constants of Organic Bases in Aqueous Solution, Butterworths, London, 1965; Supplement, 1972.
2. Serjeant, E.P., and Dempsey, B., Ionization Constants of Organic Acids in Aqueous Solution, Pergamon, Oxford, 1979.
3. Albert, A., “Ionization Constants of Heterocyclic Substances”, in Katritzky, A.R., Ed., Physical Methods in Heterocyclic Chemistry, Academic 4. Sober, H.A., Ed., CRC Handbook of Biochemistry, CRC Press, Boca Raton, FL, 1968.
5. Perrin, D.D., Dempsey, B., and Serjeant, E.P., pKa Prediction for Organic Acids and Bases, Chapman and Hall, London, 1981.
6. Albert, A., and Serjeant, E. P., The Determination of Ionization Constants, Third Edition, Chapman and Hall, London, 1984.
7. Budavari, S., Editor, The Merck Index, Twelth Edition, Merck & Co., Whitehouse Station, NJ, 1996.
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES (continued)
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES (continued)
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES (continued)
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES (continued)
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
N-(N-Glycylglycyl)glycine 1 DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES (continued)
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES (continued)
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES (continued)
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES (continued)
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES (continued)
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
DISSOCIATION CONSTANTS OF ORGANIC ACIDS AND BASES (continued)
Mol. Form.
t/°C
pKa
Mol. Form.
t/°C
pKa
SOLUBILITY PRODUCT CONSTANTS
The solubility product constant Ksp is a useful parameter for calculating the aqueous solubility of sparingly soluble compounds under various conditions. It may be determined by direct measurement or calculated from the standard Gibbs energies of formation ∆fG° of the species involved attheir standard states. Thus if Ksp = [M+]m [A–]n is the equilibrium constant for the reaction MmAn(s) 1 mM+(aq) + nA– (aq), where MmAn is the slightly soluble substance and M+ and A- are the ions produced in solution by the dissociation of MmAn, then the Gibbs energy changeis ∆G° = m ∆fG° (M+,aq) + n ∆fG° (A–,aq) -∆fG° (MmAn, s) The solubility product constant is calculated from the equation ln Ksp = -∆ G°/RT The first table below gives selected values of Ksp at 25°C. Many of these have been calculated from standard state thermodynamic data in References 1 and 2; other values are taken from publications of the IUPAC Solubility Data Project (References 3 to 7).
The above formulation is not convenient for treating sulfides because the S-2 ion is usually not present in significant concentrations (see Reference 8). This is due to the hydrolysis reaction which is strongly shifted to the right except in very basic solutions. Furthermore, the equilibrium constant for this reaction, which depends on the secondionization constant of H2S, is poorly known. Therefore it is more useful in the case of sulfides to define a different solubility product Kspa based onthe reaction MmSn(s) + 2H+ 1 mM+ + nH2S (aq) Values of Kspa , taken from Reference 8, are given for several sulfides in the auxiliary table following the main table. Additional discussion of sulfideequilibria may be found in References 7 and 9.
REFERENCES
1. Wagman, D.D., Evans, W.H., Parker, V.B., Schumm, R.H., Halow, I., Bailey, S.M., Churney, K.L., and Nuttall, R L., The NBS Tables of Chemical Thermodynamic Properties, J. Phys. Chem. Ref. Data, Vol. 11, Suppl. 2, 1982.
2. Garvin, D., Parker, V.B., and White, H.J., CODATA Thermodynamic Tables, Hemisphere, New York, 1987.
3. Solubility Data Series (53 Volumes), International Union of Pure and Applied Chemistry, Pergamon Press, Oxford, 1979—1992.
4. Clever, H.L., and Johnston, F.J., J. Phys. Chem. Ref. Data, 9, 751, 1980.
5. Marcus, Y., J. Phys. Chem. Ref. Data, 9, 1307, 1980.
6. Clever, H.L., Johnson, S.A., and Derrick, M.E., J. Phys. Chem. Ref. Data, 14, 631, 1985.
7. Clever, H.L., Johnson, S.A., and Derrick, M.E., J. Phys. Chem. Ref. Data, 21, 941, 1992.
8. Myers, R.J., J. Chem. Educ., 63, 687, 1986.
9. Licht, S., J. Electrochem. Soc.,135, 2971, 1988.
Compound
Ksp
SOLUBILITY PRODUCT CONSTANTS (continued)
Compound
Ksp
SOLUBILITY PRODUCT CONSTANTS (continued)
Compound
Ksp
SOLUBILITY PRODUCT CONSTANTS (continued)
Compound
Ksp
Sulfides
Compound
Kspa

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