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Solubility product constants

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

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

MmAn(s) = mMn+(aq) + nAm-(aq)

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

Ksp = [Mn+]m * [Am-]n

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

Δ = mfG°(M+, aq) + nf(A-, aq) - Δf(MmAn, s)        and       ln Ksp = -ΔG°/RT

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

For sulfides, a Kspa is defined based on the equation

MmSn(s) + 2H+  =  mM+(aq) + nH2S(aq)

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

Name Formula Ksp Kspa
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 Li3PO4 2.37*10-11
Magnesium ammonium phosphate MgNH4PO4 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 AgC2H3O2 1.94*10-3
Silver(I) arsenate Ag3AsO4 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 Ag3PO4 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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