Hydrolysis constant

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 Mesmer, 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 Mesmer, 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

Boron

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

Reaction Baes and Mesmer, 1976[5] NIST46[6]
B(OH)3 + H2O ⇌ Be(OH)4+ + H+ –9.236 –9.236 ± 0.002
2 B(OH)3 ⇌ B2(OH)5– + H+ –9.36 –9.306
3 B(OH)3 ⇌ B3O3(OH)4– + H+ + 2 H2O –7.03 –7.306
4 B(OH)3 ⇌ B4O5(OH)42– + 2 H+ + 3 H2O –16.3 –15.032

Calcium

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

Reaction Baes and Mesmer, 1976[1] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[7]
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

Chromium(II)

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

Reaction NIST46[6] Ball and Nordstrom, 1988[8]
Cr2+ + H2O ⇌ CrOH+ + H+ –5.5
Cr(OH)2(s) ⇌ Cr2+ + 2 OH– –17 ± 0.02

Chromium(III)

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

Reaction Baes and Mesmer, 1976[9] Rai et al., 1987[10] Ball and Nordstrom, 1988[8] Brown and Ekberg, 2016[11]
Cr3+ + H2O ⇌ CrOH2+ + H+ –4.0 –3.57 ± 0.08 –3.60 ± 0.07
Cr3+ + 2 H2O ⇌ Cr(OH)2+ + 2 H+ –9.7 –9.84 –9.65 ± 0.20
Cr3+ + 3 H2O ⇌ Cr(OH)3 + 3 H+ –18 –16.19 –16.25 ± 0.19
Cr3+ + 4 H2O ⇌ Cr(OH)4- + 4 H+ –27.4 –27.65 ± 0.12 –27.56 ± 0.21
2 Cr3+ + 2 H2O ⇌ Cr2(OH)24+ + 2 H+ –5.06 –5.0 –5.29 ± 0.16
3 Cr3+ + 4 H2O ⇌ Cr3(OH)45+ + 4 H+ –8.15 –10.75 ± 0.15 –9.10 ± 0.14
Cr(OH)3(s) + 3 H+ ⇌ Cr3+ + 3 H2O 12 9.35 9.41 ± 0.17
Cr2O3(s) + 6 H+ ⇌ 2 Cr3+ + 3 H2O 8.52
CrO1.5(s) + 3 H+ ⇌ Cr3+ + 1.5 H2O 7.83 ± 0.10

Chromium(VI)

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

Reaction Baes and Mesmer, 1976[12] Ball and Nordstrom, 1998[8]
CrO42– + H+ ⇌ HCrO4– 6.51 6.55 ± 0.04
HCrO4– + H+ ⇌ H2CrO4 –0.20
CrO42– + 2 H+ ⇌ H2CrO4 6.31
2 HCrO4– ⇌ Cr2O72– + H2O 1.523
2 CrO42– + 2 H+ ⇌ Cr2O72– + H2O 14.7 ± 0.1

Cobalt(II)

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

Reaction Baes and Mesmer, 1976[13] Brown and Ekberg, 2016[14]
Co2+ + H2O ⇌ Co(OH)+ + H+ –9.65 −9.61 ± 0.17
Co2+ + 2 H2O ⇌ Co(OH)2 + 2 H+ –18.8 −19.77 ± 0.11
Co2+ + 3 H2O ⇌ Co(OH)3– + 3 H+ –31.5 −32.01 ± 0.33
Co2+ + 4 H2O ⇌ Co(OH)42– + 4 H+ –46.3
2 Co2+ + H2O ⇌ Co2(OH)3+ + H+ –11.2
4 Co2+ + 4 H2O ⇌ Co4(OH)44+ + 4H+ –30.53
Co(OH)2(s) + 2 H+ ⇌ Co2+ + 2 H2O 12.3 13.24 ± 0.12
CoO(s) + 2 H+ ⇌ Co2+ + H2O 13.71 ± 0.10

Cobalt(III)

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

Reaction Brown and Ekberg, 2016[15]
Co3+ + H2O ⇌ Co(OH)2+ + H+ −1.07 ± 0.11

Copper(I)

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

Reaction Brown and Ekberg, 2016[16]
Cu+ + H2O ⇌ Cu(OH) + H+ –7.8 ± 0.4
Cu+ + 2 H2O ⇌ Cu(OH)2– + 2 H+ –18.6 ± 0.6

Copper(II)

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

Reaction Baes and Mesmer, 1976[17] NIST46[6] Plyasunova et al., 1997[18] Powell et al., 2007[19] Brown and Ekberg, 2016[16]
Cu2+ + H2O ⇌ CuOH+ + H+ < –8 –7.7 –7.97 ± 0.09 –7.95 ± 0.16 –7.64 ± 0.17
Cu2+ + 2 H2O ⇌ Cu(OH)2 + 2 H+ (< –17.3) –17.3 –16.23 ± 0.15 –16.2 ± 0.2 –16.24 ± 0.03
Cu2+ + 3 H2O ⇌ Cu(OH)3– + 3 H+ (< –27.8) –27.8 –26.63 ± 0.40 –26.60 ± 0.09 –26.65 ± 0.13
Cu2+ + 4 H2O ⇌ Cu(OH)42– + 4 H+ –39.6 –39.6 –39.73 ± 0.17 –39.74 ± 0.18 –39.70 ± 0.19
2 Cu2+ + H2O ⇌ Cu2(OH)3+ + H+ –6.71 ± 0.30 –6.40 ± 0.12 –6.41 ± 0.17
2 Cu2+ + 2 H2O ⇌ Cu2(OH)22+ + 2 H+ –10.36 –10.3 –10.55 ± 0.17 –10.43 ± 0.07 –10.55 ± 0.02
3 Cu2+ + 4 H2O ⇌ Cu3(OH)42+ + 4 H+ –20.95 ± 0.30 –21.1 ± 0.2 –21.2 ± 0.4
CuO(s) + 2 H+ ⇌ Cu2+ + H2O 7.62 7.64 ± 0.06 7.64 ± 0.06 7.63 ± 0.05
Cu(OH)2(s) + 2 H+ ⇌ Cu2+ + 2 H2O 8.67 ± 0.05 8.68 ± 0.10

Gadolinium

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

Reaction Baes and Mesmer, 1976[20] Brown and Ekberg, 2016[21]
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 Mesmer, 1976[22] Smith et al., 2003[23] Brown and Ekberg, 2016[24]
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

Germanium

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

Reaction Baes and Mesmer, 1976[25] Wood and Samson, 2006[26] Filella and May, 2023[27]
Ge(OH)4 ⇌ GeO(OH)3- + H+ –9.31 –9.32 ± 0.05 –9.099
Ge(OH)4 ⇌ GeO2(OH)22+ + 2 H+ –21.9
GeO2(OH)22– + H+ ⇌ GeO(OH)3– 12.76
8 Ge(OH)4 ⇌ Ge8O16(OH)33- + 13 H2O + 3 H+ –14.24
8 Ge(OH)4 + 3 OH– ⇌ Ge8(OH)353– 28.33
GeO2(s, hexa) + 2 H2O ⇌ Ge(OH)4 –1.35 –1.373
GeO2(s, tetra) + 2 H2O ⇌ Ge(OH)4 -4.37 –5.02 –4.999

Iron(II)

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

Reaction Baes and Mesmer, 1976[28] Nordstrom et al., 1990[2] Hummel et al., 2002[29] Lemire et al., 2013[30] Brown and Ekberg, 2016[31]
Fe2+ + H2O ⇌ FeOH+ + H+ –9.3 ± 0.5 –9.5 –9.5 –9.1 ± 0.4 −9.43 ± 0.10
Fe2+ + 2 H2O ⇌ Fe(OH)2 + 2 H+ –20.5 ± 1.0 −20.52 ± 0.08
Fe2+ + 3 H2O ⇌ Fe(OH)3- + 3 H+ –29.4 ± 1.2 −32.68 ± 0.15
Fe(OH)2(s) +2 H+ ⇌ Fe2+ + 2 H2O 12.27 ± 0.88

Lithium

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

Reaction Baes and Mesmer, 1976[32] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[33]
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 Mesmer, 1976[34] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[35]
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

Manganese(II)

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

Reaction Perrin et al., 1969[36] Baes and Mesmer, 1976[37] Nordstrom et al., 1990[2] Hummel et al., 2002[29] Brown and Ekberg, 2016[38]
Mn2+ + H2O ⇌ MnOH+ + H+ –10.59 –10.59 –10.59 –10.59 −10.58 ± 0.04
Mn2+ + 2 H2O ⇌ Mn(OH)2 + 2 H+ –22.2 −22.18 ± 0.20
Mn2+ + 3 H2O ⇌ Mn(OH)3– + 3 H+ –34.8 −34.34 ± 0.45
Mn2+ + 4 H2O ⇌ Mn(OH)42– + 4 H+ –48.3 −48.28 ± 0.40
2 Mn2+ + H2O ⇌ Mn2OH3+ + H+ –10.56
2 Mn2+ + 3 H2O ⇌ Mn2(OH)3+ + 6 H+ –23.90
Mn(OH)2(s) + 2 H+ ⇌ Mn2+ + 2 H2O 15.2 15.2 15.2 15.19 ± 0.10
MnO(s) + 2 H+ ⇌ Mn2+ + H2O 17.94 ± 0.12

Manganese(III)

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

Reaction Brown and Ekberg, 2016[39]
Mn3+ + H2O ⇌ MnOH2+ + H+ –11.70 ± 0.04

Nickel(II)

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

Reaction Feitknecht and Schindler, 1963[40] Baes and Messmer, 1976[41] NIST46[6] Gamsjäger et al., 2005[42] Thoenen et al., 2014[43] Brown and Ekberg, 2016[44]
Ni2+ + H2O ⇌ NiOH+ + H+ –9.86 –9.9 –9.54 ± 0.14 –9.54 ± 0.14 –9.90 ± 0.03
Ni2+ + 2 H2O ⇌ Ni(OH)2 + 2 H+ –19 –19 < –18 –21.15 ± 0.0
Ni2+ + 3 H2O ⇌ Ni(OH)3– + 3 H+ –30 –30 –29.2 ± 1.7 –29.2 ± 1.7
Ni2+ + 4 H2O ⇌ Ni(OH)42– + 4 H+ < –44
2 Ni2+ + H2O ⇌ Ni2(OH)3+ + H+ –10.7 –10.6 ± 1.0 –10.6 ± 1.0 –10.6 ± 1.0
4 Ni2+ + 4 H2O ⇌ Ni4(OH)44+ + 4 H+ –27.74 –27.7 –27.52 ± 0.15 –27.52 ± 0.15 –27.9 ± 0.6
β-Ni(OH)2(s) + 2 H+ ⇌ Ni2+ + 2 H2O 10.8 11.02 ± 0.20 10.96 ± 0.20

11.75 ± 0.13 (microcr)

Ni(OH)2(s) ⇌ Ni2+ + 2 OH– –17.2 (inactive) –17.2 –16.97± 0.20 (β)

–17.2 ± 1.3 (cr)
Ni(OH)2(s) + OH– ⇌ Ni(OH)3– –4.2 (inactive)
NiO(cr) + 2 H+ ⇌ Ni2+ + H2O 12.38 ± 0.06 12.48 ± 0.15

Potassium

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

Reaction Baes and Mesmer, 1976[32] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[45]
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

Scandium

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

Reaction Baes and Mesmer, 1976[46] Brown and Ekberg, 2016[47]
Sc3+ + H2O ⇌ ScOH2+ + H+ –4.3 –4.16 ± 0.05
Sc3+ + 2 H2O ⇌ Sc(OH)2+ + 2 H+ –9.7 –9.71 ± 0.30
Sc3+ + 3 H2O ⇌ Sc(OH)3 + 3 H+ –16.1 –16.08 ± 0.30
Sc3+ + 4 H2O ⇌ Sc(OH)4–+ 4 H+ –26 –26.7 ± 0.3
2 Sc3+ + 2 H2O ⇌ Sc2(OH)24+ + 2 H+ –6.0 –6.02 ± 0.10
3 Sc3+ + 5 H2O ⇌ Sc3(OH)54+ + 5 H+ –16.34 –16.33 ± 0.10
Sc(OH)3(s) + 3 H+ ⇌ Sc3+ + 3 H2O 9.17 ± 0.30
ScO1.5(s) + 3 H+ ⇌ Sc3+ + 1.5 H2O 5.53 ± 0.30
ScO(OH)(c) + 3 H+ ⇌ Sc3+ + 2 H2O 9.4
Sc(OH)3(c) + OH– ⇌ Sc(OH)4 –3.5 ± 0.2

Selenium(–II)

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

Reaction Olin et al., 2015[48] Thoenen et al., 2014[43]
H2Se(g) ⇌ H2Se(aq) –1.10 ± 0.01 –1.10 ± 0.01
H2Se ⇌ HSe– + H+ –3.85 ± 0.05 –3.85 ± 0.05
HSe– ⇌ Se2– + H+ –14.91 ± 0.20

Selenium(IV)

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

Reaction Baes and Mesmer, 1976[49] Olin et al., 2005[48] Thoenen et al., 2014[43]
SeO32– + H+ ⇌ HSeO3– 8.50 8.36 ± 0.23 8.36 ± 0.23
HSeO3– + H+ ⇌ H2SeO3 2.75 2.64 ± 0.14 2.64 ± 0.14

Selenium(VI)

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

Reaction Baes and Mesmer, 1976[50] Olin et al., 2005[48] Thoenen et al., 2014[43]
SeO42‒ + H+ ⇌ HSeO4‒ 1.360 1.75 ± 0.10 1.75 ± 0.10

Silicon

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

Reaction Baes and Mesmer, 1976[51] Thoenen et al., 2014[43]
Si(OH)4 ⇌ SiO(OH)3– + H+ –9.86 –9.81 ± 0.02
Si(OH)4 ⇌ SiO2(OH)22– + 2 H+ –22.92 –23.14 ± 0.09
4 Si(OH)4 ⇌ Si4O6(OH)64– + 2 H+ + 4 H2O –13.44
4 Si(OH)4 ⇌ Si4O8(OH)44– + 4 H+ + 4 H2O –35.80 –36.3 ± 0.2
SiO2(quartz) + 2 H2O ⇌ Si(OH)4 –4.0 –3.739 ± 0.087
SiO2(am) + 2 H2O ⇌ Si(OH)4 –2.714

Sodium

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

Reaction Baes and Mesmer, 1976[32] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[52]
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 Mesmer, 1976[1] Nordstrom et al., 1990[2] Brown and Ekberg, 2016[53]
Sr2+ + H2O ⇌ SrOH+ + H+ –13.29 –13.29 –13.15 ± 0.05

Titanium(III)

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

Reaction Perrin et al., 1969[54] Baes and Mesmer, 1976[55] Brown and Ekberg, 2016[56]
Ti3+ + H2O ⇌ TiOH2+ + H+ –1.29 –2.2 –1.65 ± 0.11
2 Ti3+ + 2 H2O ⇌ Ti2(OH)24+ + 2 H+ –3.6 –2.64 ± 0.10

Titanium(IV)

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

Reaction Baes and Mesmer, 1976[55] Brown and Ekberg, 2016[56]
Ti(OH)22+ + H2O ⇌ Ti(OH)3+ + H+ ⩽–2.3
Ti(OH)22+ + 2 H2O ⇌ Ti(OH)4 + 2 H+ –4.8
TiO2+ + H2O ⇌ TiOOH+ + H+ –2.48 ± 0.10
TiO2+ + 2 H2O ⇌ TiO(OH)2 + 2 H+ –5.49 ± 0.14
TiO2+ + 3 H2O ⇌ TiO(OH)3– + 3 H+ –17.4 ± 0.5
TiO(OH)2 + H2O ⇌ TiO(OH)3– + H+ –11.9 ±0.5
TiO2(c) +2 H2O ⇌ Ti(OH)4 ~ –4.8
TiO2(s) + H+ ⇌ TiOOH+ –6.06 ± 0.30
TiO2(s) + H2O ⇌ TiO(OH)2 –9.02 ± 0.02
TiO2 x H2O ⇌ Ti(OH)22+[OH–]
TiO2(s) + 4 H+ ⇌ Ti4+ + 2 H2O –3.56 ± 0.10

Vanadium(IV)

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

Reaction Brown and Ekberg, 2016[39]
VO2+ + H2O ⇌ VO(OH)+ + H+ –5.30 ± 0.13
2 VO2+ + 2 H2O ⇌ (VO)2(OH)22+ + 2 H+ –6.71 ± 0.10

Vanadium(V)

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

Reaction Baes and Mesmer, 1976[57] Brown and Ekberg, 2016[58]
VO2+ + 2 H2O ⇌ VO(OH)3 + H+ –3.3
VO2+ + 2 H2O ⇌ VO2(OH)2– + 2 H+ –7.3 –7.18 ± 0.12
10 VO2+ + 8 H2O ⇌ V10O26(OH)24– + 14 H+ –10.7
VO2(OH)2– ⇌ VO3(OH)2– + H+ –8.55
2 VO2(OH)2– ⇌ V2O6(OH)23– + H+ + H2O –6.53
VO3(OH)2– ⇌ VO43– + H+ –14.26
2 VO3(OH)2– ⇌ V2O74– + H2O 0.56
3 VO3(OH)2– + 3 H+⇌ V3O93– + 3 H2O 31.81
V10O26(OH)24– ⇌ V10O27(OH)5– + 3 H+ –3.6
V10O27(OH)5– ⇌ V10O286– + H+ –6.15
VO2+ + H2O ⇌ VO2OH + H+ –3.25 ± 0.1
VO2+ + 3 H2O ⇌ VO2(OH)32- + 3 H+ –15.74 ± 0.19
VO2+ + 4 H2O ⇌ VO2(OH)43- + 4 H+ –30.03 ± 0.24
2 VO2+ + 4 H2O ⇌ (VO2)2(OH)42- + 4 H+ –11.66 ± 0.53
2 VO2+ + 5 H2O ⇌ (VO2)2(OH)53- + 5 H+ –20.91 ± 0.22
2 VO2+ + 6 H2O ⇌ (VO2)2(OH)64- + 6 H+ –32.43 ± 0.30
4 VO2+ + 8 H2O ⇌ (VO2)4(OH)84- + 8 H+ –20.78 ± 0.33
4 VO2+ + 9 H2O ⇌ (VO2)4(OH)95- + 9 H+ –31.85 ± 0.26
4 VO2+ + 10 H2O ⇌ (VO2)4(OH)106- + 10 H+ –45.85 ± 0.26
5 VO2+ + 10 H2O ⇌ (VO2)5(OH)105- + 10 H+ –27.02 ± 0.34
10 VO2+ + 14 H2O ⇌ (VO2)10(OH)144- + 14 H+ –10.5 ± 0.3
10 VO2+ + 15 H2O ⇌ (VO2)10(OH)155- + 15 H+ –15.73 ± 0.33
10 VO2+ + 16 H2O ⇌ (VO2)10(OH)166- + 16 H+ –23.90 ± 0.35
½ V2O5(c) + H+ ⇌ VO2+ + ½ H2O –0.66
V2O5(s) + 2 H+ ⇌ 2 VO2+ + H2O –0.64 ± 0.09

Yttrium

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

Reaction Baes and Mesmer, 1976[59] Brown and Ekberg, 2016[60]
Y3+ + H2O ⇌ YOH2+ + H+ –7.7 –7.77 ± 0.06
Y3+ + 2 H2O ⇌ Y(OH)2+ + 2 H+ (–16.4) [Estimation]
Y3+ + 3 H2O ⇌ Y(OH)3 + 3 H+ (–26.0) [Estimation]
Y3+ + 4 H2O ⇌ Y(OH)4-+ 4 H+ –36.5
2 Y3+ + 2 H2O ⇌ Y2(OH)24+ + 2 H+ –14.23 –14.1 ± 0.2
3 Y3+ + 5 H2O ⇌ Y3(OH)54+ + 5 H+ –31.6 –32.7 ± 0.3
Y(OH)3(s) + 3 H+ ⇌ Y3+ + 3 H2O 17.5 17.32 ± 0.30

Zinc

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

Reaction Baes and Mesmer, 1976[61] Powell and Brown, 2013[62] Brown and Ekberg, 2016[63]
Zn2+ + H2O ⇌ ZnOH+ + H+ −8.96 −8.96 ± 0.05 −8.94 ± 0.06
Zn2+ + 2 H2O ⇌ Zn(OH)2 + 2 H+ −16.9 –17.82 ± 0.08 −17.89 ± 0.15
Zn2+ + 3 H2O ⇌ Zn(OH)3- + 3 H+ −28.4 –28.05 ± 0.05 −27.98 ± 0.10
Zn2+ + 4 H2O ⇌ Zn(OH)42- + 4 H+ −41.2 –40.41 ± 0.12 −40.35 ± 0.22
2 Zn2+ + H2O ⇌ Zn2OH3+ + H+ −9.0 –7.9 ± 0.2 −7.89 ± 0.31
2 Zn2+ + 6 H2O ⇌ Zn2(OH)62- + 6 H+ −57.8
ZnO(s) + 2 H+ ⇌ Zn2+ + H2O 11.14 11.12 ± 0.05 11.11 ± 0.10
ε-Zn(OH)2(s) + 2 H+ ⇌ Zn2+ + 2 H2O 11.38 ± 0.20 11.38± 0.20
β1-Zn(OH)2(s) + 2 H+ ⇌ Zn2+ + 2 H2O 11.72 ± 0.04
β2-Zn(OH)2(s) + 2 H+ ⇌ Zn2+ + 2 H2O 11.76 ± 0.04
γ-Zn(OH)2(s) + 2 H+ ⇌ Zn2+ + 2 H2O 11.70 ± 0.04
δ-Zn(OH)2(s) + 2 H+ ⇌ Zn2+ + 2 H2O 11.81 ± 0.04

Zirconium

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

Reaction Baes and Mesmer, 1976[64] Thoenen et al., 2014[43] Brown and Ekberg, 2016[65]
Zr4+ + H2O ⇌ ZrOH3+ + H+ 0.32 0.32 ± 0.22 0.12 ± 0.12
Zr4+ + 2 H2O ⇌ Zr(OH)22+ + 2 H+ (−1.7)* 0.98 ± 1.06* −0.18 ± 0.17*
Zr4+ + 3 H2O ⇌ Zr(OH)3+ + 3 H+ (−5.1)
Zr4+ + 4 H2O ⇌ Zr(OH)4 + 4 H+ –9.7* –2.19 ± 0.70* −4.53 ± 0.37*
Zr4+ + 5 H2O ⇌ Zr(OH)5– + 5 H+ –16.0
Zr4+ + 6 H2O ⇌ Zr(OH)62– + 6 H+ –29± 0.70 –30.5 ± 0.3
3 Zr4+ + 4 H2O ⇌ Zr3(OH)48+ + 4 H+ –0.6 0.4 ± 0.3 0.90 ± 0.18
3 Zr4+ + 5 H2O ⇌ Zr3(OH)57+ + 5 H+ 3.70
3 Zr4+ + 9 H2O ⇌ Zr3(OH)93+ + 9 H+ 12.19 ± 0.20 12.19 ± 0.20
4 Zr4+ + 8 H2O ⇌ Zr4(OH)88+ + 8 H+ 6.0 6.52 ± 0.05 6.52 ± 0.05
4 Zr4+ + 15 H2O ⇌ Zr4(OH)15+ + 15 H+ 12.58± 0.24
4 Zr4+ + 16 H2O ⇌ Zr4(OH)16 + 16 H+ 8.39± 0.80
ZrO2(s) + 4 H+ ⇌ Zr4+ + 2 H2O –1.9* –5.37 ± 0.42*
ZrO2(s, baddeleyite) + 4 H+ ⇌ Zr4+ + 2 H2O –7 ± 1.6
ZrO2(am) + 4 H+ ⇌ Zr4+ + 2 H2O –3.24± 0.10 –2.97 ± 0.18

*Errors in compilations concerning equilibrium and/or data elaboration. Data not recommended. It is strongly suggested to refer to the original papers.

References
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