Hydrolysis constant

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The word hydrolysis is applied to chemical reactions in which a substance reacts with water. In organic chemistry, the products of the reaction are usually molecular, being formed by combination with H and OH groups (e.g., hydrolysis of an ester to an alcohol and a carboxylic acid). In inorganic chemistry, the word most often applies to cations forming soluble hydroxide or oxide complexes with, in some cases, the formation of hydroxide and oxide precipitates.

Metal hydrolysis and associated equilibrium constant values

The hydrolysis reaction for a hydrated metal ion in aqueous solution can be written as:

p Mz+ + q H2O = Mp(OH)q(pz–q) + q H+

and the corresponding formation constant as:

and associated equilibria can be written as:

MOx(OH)z–2x(s) + z H+ = Mz+ + (z–x) H2O
MOx(OH)z–2x(s) + x H2O = Mz+ + z OH−
p MOx(OH)z–2x(s) + (pz–q) H+ = Mp(OH)q(pz–q) + (pz–px–q) H2O

Barium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Baes and Messmer, 1976[1] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[3]
Ba2+ + H2O = BaOH+ + H+ –13.47 –13.47 –13.32 ± 0.07

Beryllium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Baes and Messmer, 1976[4]
Be2+ + H2O = BeOH+ + H+ –5.10
Be2+ + 2 H2O = Be(OH)2 + 2 H+ –23.65
Be2+ + 3 H2O = Be(OH)3– + 3 H+ –23.25
Be2+ + 4 H2O = Be(OH)42– + 4 H+ –37.42
2 Be2+ + H2O = Be2OH3+ + H+ –3.97
3 Be2+ + 3 H2O = Be3(OH)33+ + 3 H+ –8.92
6 Be2+ + 8 H2O = Be6(OH)84+ + 8 H+ –27.2
α-Be(OH)2(cr) + 2 H+ = Be2+ + 2 H2O 6.69

Calcium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Baes and Messmer, 1976[1] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[5]
Ca2+ + H2O = CaOH+ + H+ –12.85 –12.78 –12.57 ± 0.03
Ca(OH)2(cr) + 2 H+ = Ca2+ + 2 H2O 22.80 22.8 22.75 ± 0.02

Gadolinium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Baes and Messmer, 1976[6] Brown and Ekberg, 2016[7]
Gd3+ + H2O = GdOH2+ + H+ –8.0 –7.87 ± 0.05
Gd3+ + 2 H2O = Gd(OH)2+ + 2 H+ (–16.4)
Gd3+ + 3 H2O = Gd(OH)3 + 3 H+ (–25.2)
Gd3+ + 4 H2O = Gd(OH)4– + 4 H+ –34.4
2 Gd3+ + 2 H2O = Gd2(OH)24+ + 2 H+ –14.16 ± 0.20
3 Gd3+ + 5 H2O = Gd3(OH)54+ + 5 H+ –33.0 ± 0.3
Gd(OH)3(s) + 3 H+ = Gd3+ + 3 H2O 15.6 17.20 ± 0.48
Gd(OH)3(c) + OH– = Gd(OH)4– –4.8 ± 0.3
Gd(OH)3(c) = Gd(OH)3 –9.6

Gallium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Baes and Messmer, 1976[8] Smith et al., 2003[9] Brown and Ekberg, 2016[10]
Ga3+ + H2O = GaO)2+ + H+ –2.6 –2.897 –2.74
Ga3+ + 2 H2O = Ga(OH)2+ + 2 H+ –5.9 –6.694 –7.0
Ga3+ + 3 H2O = Ga(OH)3 + 3 H+ –10.3 –11.96
Ga3+ + 4 H2O = Ga(OH)4– + 4 H+ –16.6 –16.588 –15.52
Ga(OH)3(s) = Ga3+ + 3 OH– –37 –37.0
GaO(OH)(s) + H2O = Ga3+ + 3 OH– –39.06 –39.1 –40.51

Lithium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Baes and Messmer, 1976[11] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[12]
Li+ + H2O = LiOH + H+ –13.64 ± 0.06 –13.64 –13.84 ± 0.14

Magnesium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Baes and Messmer, 1976[13] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[14]
Mg2+ + H2O = MgOH+ + H+ –11.44 –11.44 –11.70 ± 0.04
4 Mg2+ + 4 H2O = Mg4(OH)44+ + 4 H+ –39.71
Mg(OH)2(cr) + 2 H+ = Mg2+ + 2 H2O 16.84 16.84 17.11 ± 0.04

Potassium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Baes and Messmer, 1976[11] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[15]
K+ + H2O = KOH + H+ –14.46 ± 0.4 –14.46 –14.5 ± 0.4

Radium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Nordstrom et al., 1990[2]
Ra2+ + H2O = RaOH+ + H+ –13.49

Sodium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Baes and Messmer, 1976[11] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[16]
Na+ + H2O = NaOH + H+ –14.18 ± 0.25 –14.18 –14.4 ± 0.2

Strontium

Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:

Reaction Baes and Messmer, 1976[1] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[17]
Sr2+ + H2O = SrOH+ + H+ –13.29 –13.29 –13.15 ± 0.05

References

  1. ^ a b c Baes, C.F.; Messmer, R.E. (1976). The Hydrolysis of Cations. New York: Wiley. p. 103.
  2. ^ a b c d e f g h Nordstrom, D.K.; Plummer, L.N.; Langmuir, D.; Busenberg, E.; May, H.M.; Jones, B.F.; Parkhurst, D.L. (1990). Melchior, D.C.; Basset, R.L. (eds.). Revised chemical equilibrium data for major water-mineral reactions and their limitations. In: Chemical Modeling of Aqueous Systems II. Washington, DC: ACS. pp. 398–446.
  3. ^ Brown, P.L.; Ekberg, C. (2016). Hydrolysis of Metal Ions. New York: Wiley. pp. 213–217.
  4. ^ Baes, C.F.; Messmer, R.E. (1976). The Hydrolysis of Cations. New York: Wiley. p. 95.
  5. ^ Brown, P.L.; Ekberg, C. (2016). Hydrolysis of Metal Ions. Weinheim, Germany: Wiley. pp. 195–210.
  6. ^ Baes, C.F.; Messmer, R.E. (1976). The Hydrolysis of Cations. New York: Wiley. p. 137.
  7. ^ Brown, P.L.; Ekberg, C. (2016). Hydrolysis of Metal Ions. Wiley. pp. 284–287.
  8. ^ Baes, C.F.; Messmer, R.E. (1976). The Hydrolysis of Cations. New York: Wiley. p. 319.
  9. ^ Smith, R.M.; Martell, A.E.; Motekaitis, R.J. (2003). NIST Critically Selected Stability Constants of Metal Complexes Database, Version 7.0, NIST Standard Reference Database 46. Gaithersburg, MD, USA: National Institute of Standards, U.S. Dept. of Commerce.
  10. ^ Brown, P.L.; Ekberg, C. (2016). Hydrolysis of Metal Ions. Weinheim, Germany: Wiley. pp. 797–812.
  11. ^ a b c Baes, C.F.; Messmer, R.E. (1976). The Hydrolysis of Cations. New York: Wiley. p. 86.
  12. ^ Brown, P.L.; Ekberg, C. (2016). Hydrolysis of Metal Ions. Weinheim, Germany: Wiley. pp. 136–141.
  13. ^ Baes, C.F.; Messmer, R.E. (1976). The Hydrolysis of Cations. New York: Wiley. p. 89.
  14. ^ Brown, P.L.; Ekberg, C. (2016). Hydrolysis of Metal Ions. Weinheim, Germany: Wiley. pp. 178–195.
  15. ^ Brown, P.L.; Ekberg, C. (2016). Hydrolysis of Metal Ions. Weinheim, Germany: Wiley. pp. 148–150.
  16. ^ Brown, P.L.; Ekberg, C. (2016). Hydrolysis of Metal Ions. Weinheim, Germany: Wiley. pp. 142–147.
  17. ^ Brown, P.L.; Ekberg, C. (2016). Hydrolysis of Metal Ions. Weinheim, Germany: Wiley. pp. 210–213.


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