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 G° = m *Δf G °(M+, aq) + n *Δf G° (A-, aq) - Δf G° (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
| 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 |
