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Solubility Product Constants

The equilibrium constant, Ksp, for aqueous solutions of ionic compounds at 25°C.

For ionic compounds with limited solubility in water, an equilibrium constant, K sp , can be defined from the ion concentration in water from the equation:

M m A n (s) = m Mn+ (aq) + n Am- (aq)

where M m A n is the slightly soluble substance and Mn+ and Am- are the ions produced in solution by dissosiation of M m A n .

K sp = (Mn+) m * (Am-) n

The table below gives calculated values of K sp for common ionic substances at 25°C (77°F). They are calculated by using standard state thermodynamic data and the equations:

Δ = m f G °(M+, aq) + n f (A-, aq) - Δf (M m A n , s)        and       ln K sp = -Δ G°/RT

K sp is indicating the maximum concentration of the solved ionic substace in water at the actual (stable) temperature.


For sulfides , a K spa is defined based on the equation

M m S n (s) + 2H+= m M+(aq) + n H2S(aq)

See also Solutions, molarity and dilution, and Solubility guidelines for ionic compounds in water

Solubility Product Constants
Name Formula K sp K spa
Aluminium hydroxide Al(OH)3 3 ×10-34
Aluminium phosphate AlPO4 9.84 ×10-21
Barium bromate Ba(BrO3)2 2.43 ×10-4
Barium carbonate BaCO3 2.58 ×10 -9
Barium chromate(VI) BaCrO4 1.17 ×10-10
Barium fluoride BaF2 1.84 ×10-7
Barium hydroxide octahydrate Ba(OH)2*8H2O 2.55 ×10-4
Barium iodate Ba(IO3)2 4.01 ×10 -9
Barium iodate monohydrate Ba(IO3)2*H2O 1.67 ×10 -9
Barium molybdate BaMoO4 3.54 ×10-8
Barium nitrate Ba(NO3)2 4.64 ×10-3
Barium selenate BaSeO4 3.40 ×10-8
Barium sulfate BaSO4 1.08 ×10-10
Barium sulfite BaSO3 5.0 ×10-10
Beryllium hydroxide Be(OH)2 6.92 ×10-22
Bismuth arsenate BiAsO4 4.43 ×10-10
Bismuth iodide BiI 7.71 ×10-19
Bismuth triiodite BiI3 7.71 ×10-19
Cadmium arsenate Cd3 (AsO4 )2 2.2 ×10-33
Cadmium carbonate CdCO3 1.0 ×10-12
Cadmium fluoride CdF2 6.44 ×10-3
Cadmium hydroxide Cd(OH)2 7.2 ×10-15
Cadmium iodate Cd(IO3)2 2.5 ×10-8
Cadmium oxalate trihydrate CdC2O4 *3H2O 1.42 ×10-8
Cadmium phosphate Cd3 (PO4 )2 2.53 ×10-33
Cadmium sulfide CdS 8 ×10-7
Calcium carbonate (calcite) CaCO3 3.36 ×10 -9
Calcium carbonate (aragonite) CaCO3 6.0 ×10 -9
Calcium fluoride CaF2 3.45 ×10-11
Calcium hydroxide Ca(OH)2 5.02 ×10-6
Calcium iodate Ca(IO3)2 6.47 ×10-6
Calcium iodate hexahydrate Ca(IO3)2*6H2O 7.10 ×10-7
Calcium molybdate CaMoO4 1.46 ×10-8
Calcium oxalate monohydrate CaC2O4 *H2O 2.32 ×10 -9
Calcium phosphate Ca3 (PO4 )2 2.07 ×10-33
Calcium sulfate CaSO4 4.93 ×10-5
Calcium sulfate dihydrate CaSO4 *2H2O 3.14 ×10-5
Calcium sulfite hemihydrate CaSO3 *0.5H2O 3.1 ×10-7
Cesium perchlorate CsClO4 3.95 ×10-3
Cesium periodate CsIO4 5.16 ×10-6
Cobalt(II) arsenate Co3 (AsO4 )2 6.80 ×10-29
Cobalt(II) carbonate CoCO3 1.0 ×10-10
Cobalt(II) hydroxide Co(OH)2 5.92 ×10-15
Cobalt(II) iodate dihydrate Co(IO3)2*2H2O 1.21 ×10-2
Cobalt(II) phosphate Co3 (PO4 )2 2.05 ×10-35
Copper(II) arsenate Cu3 (AsO4 )2 7.95 ×10-36
Copper(I) bromide CuBr 6.27 ×10 -9
Copper(I) chloride CuCl 1.72 ×10-7
Copper(I) cyanide CuCN 3.47 ×10-20
Copper(II) hydroxide Cu(OH)2 1 ×10-20
Copper(II) iodate monohydrate Cu(IO3)2*H2O 6.94 ×10-8
Copper(I) iodide CuI 1.27 ×10-12
Copper(II) oxalate CuC2O4 4.43 ×10-10
Copper(II) phosphate Cu3 (PO4 )2 1.40 ×10-37
Copper(II) sulfide CuS 6 ×10-16
Copper(I) thiocyanate CuSCN 1.77 ×10-13
Chromium(II)hydroxide Cr(OH)2 1 ×10-17
Chromium(III)hydroxide Cr(OH)3 1 ×10-30
Europium(III) hydroxide Eu(OH)3 9.38 ×10-27
Gallium(III) hydroxide Ga(OH)3 7.38 ×10-36
Iron(II) carbonate FeCO3 3.13 ×10-11
Iron(II) fluoride FeF2 2.36 ×10-6
Iron(II) hydroxide Fe(OH)2 4.87 ×10-17
Iron(III) hydroxide Fe(OH)3 2.79 ×10-39
Iron(III) phosphate dihydrate FePO4 *2H2O 9.91 ×10-16
Iron(II) sulfide FeS 6 ×102
Lanthanum iodate La(IO3)3 7.50 ×10-12
Lead(II) bromide PbBr2 6.60 ×10-6
Lead(II) carbonate PbCO3 7.40 ×10-14
Lead(II) chloride PbCl2 1.70 ×10-5
Lead(II) chromate PbCrO4 3 ×10-13
Lead(II) fluoride PbF2 3.3 ×10-8
Lead(II) hydroxide Pb(OH)2 1.43 ×10-20
Lead(II) iodate Pb(IO3)2 3.69 ×10-13
Lead(II) iodide PbI2 9.8 ×10 -9
Lead oxalate PbC2O4 8.5 ×10 -9
Lead(II) selenate PbSeO4 1.37 ×10-7
Lead(II) sulfate PbSO4 2.53 ×10-8
Lead(II) sulfide PbS 3 ×10-7
Lithium carbonate LiCO3 8.15 ×10-4
Lithium fluoride LiF 1.84 ×10-3
Lithium phosphate Li3 PO4 2.37 ×10-11
Magnesium ammonium phosphate MgNH4 PO4 3 ×10-13
Magnesium carbonate MgCO3 6.82 ×10-6
Magnesium carbonate pentahydrate MgCO3 *5H2O 3.79 ×10-6
Magnesium carbonate trihydrate MgCO3 *3H2O 2.38 ×10-6
Magnesium fluoride MgF2 5.16 ×10-11
Magnesium hydroxide Mg(OH)2 5.61 ×10-12
Magnesium oxalate dihydrate MgC2O4 *2H2O 4.83 ×10-6
Magnesium phosphate Mg3 (PO4 )2 1.04 ×10-24
Manganese(II) carbonate MnCO3 2.24 ×10-11
Manganese(II) iodate Mn(IO3)2 4.37 ×10-7
Manganese(II) oxalate dihydrate MnC2O4*2H2O 1.70 ×10-7
Manganese(II) sulfide (a-form) MnS 3 ×107
Mercury(I) bromide Hg2Br2 6.40 ×10-23
Mercury(II) bromide HgBr3 6.2 ×10-20
Mercury(I) carbonate Hg2CO3 3.6 ×10-17
Mercury(I) chloride Hg2Cl2 1.43 ×10-18
Mercury(I) fluoride Hg2F2 3.10 ×10-6
Mercury(I)hydroxide Hg2(OH)2 2 ×10-24
Mercury(II) hydroxide Hg(OH)2 4 ×10-26
Mercury(I) iodide Hg2I2 5.2 ×10-29
Mercury(II) iodide (red) HgI2 2.9 ×10-29
Mercury(I) oxalate Hg2C2O4 1.75 ×10-13
Mercury(I) sulfate Hg2SO4 6.5 ×10-7
Mercury(II) sulfide (red) Hg2S 4 ×10-33
Mercury(II) sulfide (black) Hg2S 2 ×10-32
Mercury(I) thiocyanate Hg2(SCN)2 3.2 ×10-20
Neodymium carbonate Nd2(CO3)3 1.08 ×10-33
Nickel(II) carbonate NiCO3 1.42 ×10-7
Nickel(II) hydroxide Ni(OH)2 5.48 ×10-16
Nickel(II) iodate Ni(IO3)2 4.71 ×10-5
Nickel(II) phosphate Ni3 (PO4 )2 4.74 ×10-32
Palladium(II) thiocyanate Pd(SCN)2 4.39 ×10-23
Potassium hexachloroplatinate K2PtCl6 7.48 ×10-6
Potassium perchlorate KClO4 1.05 ×10-2
Potassium periodate KIO4 3.71 ×10-4
Praseodymium(III) hydroxide Pr(OH)3 3.39 ×10-24
Radium iodate Ra(IO3)2 1.16 ×10 -9
Radium sulfate RaSO4 3.66 ×10-11
Rubidium perchlorate RbClO4 3.00 ×10-3
Scandium fluoride ScF3 5.81 ×10-24
Scandium hydroxide Sc(OH)3 2.22 ×10-31
Silver(I) acetate AgC2H3 O2 1.94 ×10-3
Silver(I) arsenate Ag3 AsO4 1.03 ×10-22
Silver(I) bromate AgBrO3 5.38 ×10-5
Silver(I) bromide AgBr 5.35 ×10-13
Silver(I) carbonate Ag2CO3 8.46 ×10-12
Silver(I) chloride AgCl 1.77 ×10-10
Silver(I) chromate Ag2CrO4 1.12 ×10-12
Silver(I) cyanide AgCN 5.97 ×10-17
Silver(I) hydroxide AgOH 2 ×10-8
Silver(I) iodate AgIO3 3.17 ×10-8
Silver(I) iodide AgI 8.52 ×10-17
Silver(I) oxalate Ag2C2O4 5.40 ×10-12
Silver(I) phosphate Ag3 PO4 8.89 ×10-17
Silver(I) sulfate Ag2SO4 1.20 ×10-5
Silver(I) sulfide Ag2S 6 ×10-30
Silver(I) sulfite Ag2SO3 1.50 ×10-14
Silver(I) thiocyanate AgSCN 1.03 ×10-12
Strontium arsenate Sr3 (AsO4 ) 4.29 ×10-19
Strontium carbonate SrCO3 5.60 ×10-10
Strontium fluoride SrF2 4.33 ×10 -9
Strontium iodate Sr(IO3)2 1.14 ×10-7
Strontium iodate hexahydrate Sr(IO3)2*6H2O 4.55 ×10-7
Strontium iodate monohydrate Sr(IO3)2*H2O 3.77 ×10-7
Strontium oxalate SrC2O4 5 ×10-8
Strontium sulfate SrSO4 3.44 ×10-7
Thallium(I) bromate TlBrO3 1.10 ×10-4
Thallium(I) bromide TlBr 3.71 ×10-6
Thallium(I) chloride TlCl 1.86 ×10-4
Thallium(I) chromate Tl2CrO4 8.67 ×10-13
Thallium(III) hydroxide Tl(OH)3 1.68 ×10-44
Thallium(I) iodate TlIO3 3.12 ×10-6
Thallium(I) iodine TlI 5.54 ×10-8
Thallium(I) thiocyanate TlSCN 1.57 ×10-4
Tin(II) hydroxide Sn(OH)2 5.45 ×10-27
Tin(II) sulfide SnS 1 ×10-5
Vanadium(II) hydroxide V(OH)2 4 ×10-16
Vanadium(III) hydroxide V(OH)3 4 ×10-35
Yttrium carbonate Y2(CO3)3 1.03 ×10-31
Yttrium fluoride YF3 8.62 ×10-21
Yttrium hydroxide Y(OH)3 1.00 ×10-22
Yttrium iodate Y(IO3)3 1.12 ×10-10
Zinc arsenate Zn3 (AsO4 )2 2.8 ×10-28
Zinc carbonate ZnCO3 1.46 ×10-10
Zinc carbonate monohydrate ZnCO3 *H2O 5.42 ×10-11
Zinc fluoride ZnF2 3.04 ×10-2
Zinc hydroxide Zn(OH)2 3 ×10-17
Zinc iodate dihydrate Zn(IO3)2*2H2O 4.1 ×10-6
Zinc oxalate dihydrate ZnC2O4 *2H2O 1.38 ×10 -9
Zinc selenide ZnSe 3.6 ×10-26
Zinc selenite monohydrate ZnSeO3 *H2O 1.59 ×10-7
Zinc sulfide (sphalerite) ZnS 2 ×10-4
Zinc sulfide (wurtzite) ZnS 3 ×10-2
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