Solubility Product Constants
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 M n+ (aq) + n A m- (aq)
where M m A n is the slightly soluble substance and M n+ and A m- are the ions produced in solution by dissosiation of M m A n .
K sp = [M n+ ] m * [A m- ] 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 | AlPO 4 | 9.84 *10 -21 | |
| Barium bromate | Ba(BrO3 ) 2 | 2.43*10-4 | |
| Barium carbonate | BaCO3 | 2.58*10 -9 | |
| Barium chromate(VI) | BaCrO 4 | 1.17*10 -10 | |
| Barium fluoride | BaF 2 | 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 | BaMoO 4 | 3.54*10 -8 | |
| Barium nitrate | Ba(NO3 ) 2 | 4.64*10-3 | |
| Barium selenate | BaSeO 4 | 3.40*10 -8 | |
| Barium sulfate | BaSO 4 | 1.08*10 -10 | |
| Barium sulfite | BaSO3 | 5.0*10 -10 | |
| Beryllium hydroxide | Be(OH) 2 | 6.92*10 -22 | |
| Bismuth arsenate | BiAsO 4 | 4.43*10 -10 | |
| Bismuth iodide | BiI | 7.71*10-19 | |
| Bismuth triiodite | BiI3 | 7.71*10-19 | |
| Cadmium arsenate | Cd3 (AsO 4 ) 2 | 2.2*10 -33 | |
| Cadmium carbonate | CdCO3 | 1.0*10-12 | |
| Cadmium fluoride | CdF 2 | 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 | CdC2O 4 *3H2O | 1.42*10 -8 | |
| Cadmium phosphate | Cd3 (PO 4 ) 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 | CaF 2 | 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 | CaMoO 4 | 1.46*10 -8 | |
| Calcium oxalate monohydrate | CaC2O 4 *H2O | 2.32*10 -9 | |
| Calcium phosphate | Ca3 (PO 4 ) 2 | 2.07*10 -33 | |
| Calcium sulfate | CaSO 4 | 4.93*10 -5 | |
| Calcium sulfate dihydrate | CaSO 4 *2H2O | 3.14 *10 -5 | |
| Calcium sulfite hemihydrate | CaSO3 *0.5H2O | 3.1 *10 -7 | |
| Cesium perchlorate | CsClO 4 | 3.95*10-3 | |
| Cesium periodate | CsIO 4 | 5.16 *10-6 | |
| Cobalt(II) arsenate | Co3 (AsO 4 ) 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 (PO 4 ) 2 | 2.05*10 -35 | |
| Copper(II) arsenate | Cu3 (AsO 4 ) 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 | CuC2O 4 | 4.43*10 -10 | |
| Copper(II) phosphate | Cu3 (PO 4 ) 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 | FeF 2 | 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 | FePO 4 *2H2O | 9.91*10 -16 | |
| Iron(II) sulfide | FeS | 6*102 | |
| Lanthanum iodate | La(IO3 )3 | 7.50*10-12 | |
| Lead(II) bromide | PbBr 2 | 6.60*10-6 | |
| Lead(II) carbonate | PbCO3 | 7.40*10 -14 | |
| Lead(II) chloride | PbCl 2 | 1.70*10 -5 | |
| Lead(II) chromate | PbCrO 4 | 3*10 -13 | |
| Lead(II) fluoride | PbF 2 | 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 | PbI 2 | 9.8*10 -9 | |
| Lead oxalate | PbC2O 4 | 8.5*10 -9 | |
| Lead(II) selenate | PbSeO 4 | 1.37*10 -7 | |
| Lead(II) sulfate | PbSO 4 | 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 PO 4 | 2.37*10 -11 | |
| Magnesium ammonium phosphate | MgNH 4 PO 4 | 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 | MgF 2 | 5.16*10 -11 | |
| Magnesium hydroxide | Mg(OH) 2 | 5.61*10-12 | |
| Magnesium oxalate dihydrate | MgC2O 4 *2H2O | 4.83*10-6 | |
| Magnesium phosphate | Mg3 (PO 4 ) 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*10 7 | |
| Mercury(I) bromide | Hg2Br 2 | 6.40*10 -23 | |
| Mercury(II) bromide | HgBr3 | 6.2*10 -20 | |
| Mercury(I) carbonate | Hg2CO3 | 3.6*10 -17 | |
| Mercury(I) chloride | Hg2Cl 2 | 1.43*10 -18 | |
| Mercury(I) fluoride | Hg2F 2 | 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 | Hg2I 2 | 5.2*10 -29 | |
| Mercury(II) iodide (red) | HgI 2 | 2.9*10 -29 | |
| Mercury(I) oxalate | Hg2C2O 4 | 1.75*10 -13 | |
| Mercury(I) sulfate | Hg2SO 4 | 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 (PO 4 ) 2 | 4.74*10 -32 | |
| Palladium(II) thiocyanate | Pd(SCN) 2 | 4.39*10 -23 | |
| Potassium hexachloroplatinate | K2PtCl6 | 7.48*10-6 | |
| Potassium perchlorate | KClO 4 | 1.05*10-2 | |
| Potassium periodate | KIO 4 | 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 | RaSO 4 | 3.66*10 -11 | |
| Rubidium perchlorate | RbClO 4 | 3.00*10-3 | |
| Scandium fluoride | ScF3 | 5.81*10 -24 | |
| Scandium hydroxide | Sc(OH)3 | 2.22*10 -31 | |
| Silver(I) acetate | AgC2H3 O 2 | 1.94*10-3 | |
| Silver(I) arsenate | Ag3 AsO 4 | 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 | Ag2CrO 4 | 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 | Ag2C2O 4 | 5.40*10-12 | |
| Silver(I) phosphate | Ag3 PO 4 | 8.89*10 -17 | |
| Silver(I) sulfate | Ag2SO 4 | 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 (AsO 4 ) | 4.29*10-19 | |
| Strontium carbonate | SrCO3 | 5.60*10 -10 | |
| Strontium fluoride | SrF 2 | 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 | SrC2O 4 | 5*10 -8 | |
| Strontium sulfate | SrSO 4 | 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 | Tl2CrO 4 | 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 (AsO 4 ) 2 | 2.8*10 -28 | |
| Zinc carbonate | ZnCO3 | 1.46*10 -10 | |
| Zinc carbonate monohydrate | ZnCO3 *H2O | 5.42*10 -11 | |
| Zinc fluoride | ZnF 2 | 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 | ZnC2O 4 *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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