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, 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:
ΔG° = m*ΔfG°(M+, aq) + n*ΔfG°(A-, aq) - ΔfG°(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 |