Selected Solubility Products and
Formation Constants at 25oC
Solubility
Rules
Although all compounds have a characteristic solubility in water at a given temperature, some
families of compounds are more soluble than others and it is useful to know certain general rules
of solubility. We call any substance the solubility of which is less
than 0.01 mol/L insoluble. If its solubility is greater than 0.1 mol/L, we call it soluble. If its
solubility is between 0.01 and 0.1 mol/L, we say that it is slightly soluble. The following solubility
rules can be used to determine solubilities in water, with the disclaimer that they don't always
hold, nor do they include every ion which is in common use, but they are good to have nearby
when needed:
1. All sodium, potassium, and ammonium salts are soluble.
2. All nitrates, acetates and
perchlorates are soluble.
3. All silver, lead and mercury(I) salts are insoluble.
4. All
chlorides, bromides and iodides are soluble.
5. All carbonates, sulfides, oxides and hydroxides are insoluble.
6. All sulfates are soluble
except strontium sulfate and barium sulfate.
That having been said, here is a table of
solubility product constants.
| Compound | Formula | Ksp |
| aluminum hydroxide | Al(OH)3 | 4.6 x 10-33 |
| aluminum phosphate | AlPO4 | 6.3 x 10-19 |
| barium carbonate | BaCO3 | 5.1 x 10-9 |
| barium chromate | BaCrO4 | 2.2 x 10-10 |
| barium fluoride | BaF2 | 1.0 x 10-6 |
| barium hydroxide | Ba(OH)2 | 5 x 10-3 |
| barium iodate | Ba(IO3)2 | 1.5 x 10-9 |
| barium oxalate | BaC2O4 | 2.3 x 10-8 |
| barium sulfate | BaSO4 | 1.1 x 10-10 |
| barium sulfite | BaSO3 | 8 x 10-7 |
| barium thiosulfate | BaS2O3 | 1.6 10-5 |
| bismuthyl chloride | BiOCl | 1.8 x 10-31 |
| bismuthyl hydroxide | BiOOH | 4 x 10-10 |
| bismuth(III) sulfide | Bi2S3 | 1 x 10-97 |
| cadmium carbonate | CdCO3 | 5.2 x 10-12 |
| cadmium hydroxide | Cd(OH)2 | 2.5 x 10-14 |
| cadmium iodate | Cd(IO3)2 | 2.3 x 10-8 |
| cadmium sulfide | CdS | 8.0 x 10-27 |
| calcium carbonate | CaCO3 | 3.8 x 10-9 |
| calcium chromate | CaCrO4 | 7.1 x 10-4 |
| calcium fluoride | CaF2 | 5.3 x 10-9 |
| calcium hydroxide | Ca(OH)2 | 5.5 x 10-6 |
| calcium iodate | Ca(IO3)2 | 7.1 x 10-7 |
| calcium oxalate hydrate | CaC2O4.H2O | 1.96 x 10-8 |
| calcium hydrogen phosphate | CaHPO4 | 1 x 10-7 |
| calcium phosphate | Ca3(PO4)2 | 1 x 10-26 |
| calcium sulfate | CaSO4 | 9.1 x 10-6 |
| calcium sulfite | CaSO3 | 6.8 x 10-8 |
| chromium(II) hydroxide | Cr(OH)2 | 2 x 10-16 |
| chromium(III) hydroxide | Cr(OH)3 | 6.3 x 10-31 |
| cobalt(II) carbonate | CoCO3 | 1.4 x 10-13 |
| cobalt(III) hydroxide | Co(OH)3 | 1.6 x 10-44 |
| cobalt(II) sulfide | CoS | 4.0 x 10-21 |
| copper(I) chloride | CuCl | 1.2 x 10-6 |
| copper(I) cyanide | CuCN | 3.2 x 10-20 |
| copper(I) iodide | CuI | 1.1 x 10-12 |
| copper(I) sulfide | Cu2S | 2.5 x 10-48 |
| copper(II) arsenate | Cu3(AsO4)2 | 7.6 x 10-36 |
| copper(II) carbonate | CuCO3 | 1.4 x 10-10 |
| copper(II) chromate | CuCrO4 | 3.6 x 10-6 |
| copper(II) ferrocyanide | Cu2[Fe(CN)6] | 1.3 x 10-16 |
| copper(II) hydroxide | Cu(OH)2 | 2.2 x 10-20 |
| copper(II) sulfide | CuS | 6 x 10-37 |
| copper(II) thiocyanate | Cu(SCN)2 | 4.0 x 10-14 |
| fluorapatite | Ca5(PO4)3F | 1.0 x 10-60 |
| hydroxyapatite | Ca5(PO4)3OH | 1.0 x 10-36 |
| iron(II) carbonate | FeCO3 | 3.2 x 10-11 |
| iron(II) hydroxide | Fe(OH)2 | 8.0 x 10-16 |
| iron(II) sulfide | FeS | 6 x 10-19 |
| iron(III) arsenate | FeAsO4 | 5.7 x 10-21 |
| iron(III) ferrocyanide | Fe4[Fe(CN)6]3 | 3.3 x 10-41 |
| iron(III) hydroxide | Fe(OH)3 | 4 x 10-38 |
| iron(III) phosphate | FePO4 | 1.3 x 10-22 |
| lead(II) arsenate | Pb3(AsO4)2 | 4.0 x 10-36 |
| lead(II) azide | Pb(N3)2 | 2.5 x 10-9 |
| lead(II) bromate | Pb(BrO3)2 | 7.9 x 10-6 |
| lead(II) bromide | PbBr2 | 4.0 x 10-5 |
| lead(II) carbonate | PbCO3 | 7.4 x 10-14 |
| lead(II) chloride | PbCl2 | 1.6 x 10-5 |
| lead(II) chromate | PbCrO4 | 2.8 x 10-13 |
| lead(II) fluoride | PbF2 | 2.7 x 10-8 |
| lead(II) hydroxide | Pb(OH)2 | 1.2 x 10-5 |
| lead(II) iodate | Pb(IO3)2 | 2.6 x 10-13 |
| lead(II) iodide | PbI2 | 7.1 x 10-9 |
| lead(II) sulfate | PbSO4 | 1.6 x 10-8 |
| lead(II) sulfide | PbS | 3 x 10-29 |
| lithium carbonate | Li2CO3 | 2.5 x 10-2 |
| lithium fluoride | LiF | 3.8 x 10-3 |
| lithium phosphate | Li3PO4 | 3.2 x 10-9 |
| magnesium ammonium phosphate | MgNH4PO4 | 2.5 x 10-13 |
| magnesium arsenate | Mg3(AsO4)2 | 2.1 x 10-20 |
| magnesium carbonate | MgCO3 | 3.5 x 10-8 |
| magnesium fluoride | MgF2 | 3.7 x 10-8 |
| magnesium hydroxide | Mg(OH)2 | 1.8 x 10-11 |
| magnesium oxalate | MgC2O4 | 7 x 10-7 |
| magnesium phosphate | Mg3(PO4)2 | 1 x 10-25 |
| manganese(II) carbonate | MnCO3 | 1.8 x 10-11 |
| manganese(II) hydroxide | Mn(OH)2 | 1.9 x 10-9 |
| manganese(II) sulfide | MnS | 2.5 x 10-13 |
| mercury(I) bromide | Hg2Br2 | 5.6 x 10-23 |
| mercury(I) chloride | Hg2Cl2 | 5.0 x 10-13 |
| mercury(I) chromate | Hg2CrO4 | 2.0 x 10-9 |
| mercury(I) cyanide | Hg2(CN)2 | 5 x 10-40 |
| mercury(I) iodide | HgI2 | 4.5 x 10-29 |
| mercury(I) sulfate | Hg2SO4 | 7.4 x 10-7 |
| mercury(I) sulfide | Hg2S | 1.0 x 10-47 |
| mercury(I) thiocyanate | Hg2(SCN)2 | 3.0 x 10-20 |
| mercury(II) sulfide | HgS | 1.6 x 10-52 |
| mercury(II) thiocyanate | Hg(SCN)2 | 2.8 x 10-20 |
| nickel(II) carbonate | NiCO3 | 6.6 x 10-9 |
| nickel(II) hydroxide | Ni(OH)2 | 2.0 x 10-15 |
| nickel(II) sulfide | NiS | 3 x 10-19 |
| scandium fluoride | ScF3 | 4.2 x 10-18 |
| scandium hydroxide | Sc(OH)3 | 4.2 x 10-18 |
| silver arsenate | Ag3AsO4 | 1.0 x 10-22 |
| silver acetate | AgC2H3O2 | 2.0 x 10-3 |
| silver azide | AgN3 | 2.0 x 10-8 |
| silver benzoate | AgC7H5O2 | 2.5 x 10-5 |
| silver bromate | AgBrO3 | 5.5 x 10-5 |
| silver bromide | AgBr | 5.3 x 10-13 |
| silver carbonate | Ag2CO3 | 8.1 x 10-12 |
| silver chloride | AgCl | 1.8 x 10-10 |
| silver chromate | Ag2CrO4 | 1.1 x 10-12 |
| silver cyanide | AgCN | 1.2 x 10-16 |
| silver iodate | AgIO3 | 3.0 x 10-8 |
| silver iodide | AgI | 8.3 x 10-17 |
| silver nitrite | AgNO2 | 6.0 x 10-4 |
| silver oxalate | Ag2C2O4 | 3.6 x 10-11 |
| silver sulfate | Ag2SO4 | 1.4 x 10-5 |
| silver sulfide | Ag2S | 6 x 10-51 |
| silver sulfite | AgSO3 | 1.5 x 10-14 |
| silver thiocyanate | AgSCN | 1.0 x 10-12 |
| strontium carbonate | SrCO3 | 1.1 x 10-10 |
| strontium chromate | SrCrO4 | 2.2 x 10-5 |
| strontium fluoride | SrF2 | 2.5 x 10-9 |
| strontium oxalate | SrC2O4 | 4 x 10-7 |
| strontium sulfate | SrSO4 | 3.2 x 10-7 |
| strontium sulfite | SrSO3 | 4 x 10-8 |
| thallium(I) bromate | TlBrO3 | 1.7 x 10-4 |
| thallium(I) bromide | TlBr | 3.4 x 10-6 |
| thallium(I) chloride | TlCl | 1.7 x 10-4 |
| thallium(I) chromate | Tl2CrO4 | 9.8 x 10-15 |
| thallium(I) iodate | TlIO3 | 3.1 x 10-6 |
| thallium(I) iodide | TlI | 6.5 x 10-8 |
| thallium(I) sulfide | Tl2S | 6 x 10-22 |
| thallium(I) thiocyante | TlSCN | 1.6 x 10-4 |
| thallium(III) hydroxide | Tl(OH)3 | 6.3 x 10-46 |
| tin(II) hydroxide | Sn(OH)2 | 1.4 x 10-28 |
| tin(II) sulfide | SnS | 1 x 10-26 |
| zinc carbonate | ZnCO3 | 1.4 x 10-11 |
| zinc cyanide | Zn(CN)2 | 3 x 10-16 |
| zinc hydroxide | Zn(OH)2 | 1.2 x 10-17 |
| zinc iodate | Zn(IO3)2 | 3.9 x 10-6 |
| zinc oxalate | ZnC2O4 | 2.7 x 10-8 |
| zinc phosphate | Zn3(PO4)2 | 9.0 x 10-33 |
| zinc sulfide | ZnS | 2 x 10-25 |
| Formation Constants of Selected Complex Ions, at 25oC | Formula | Kf |
| Ag(CN)2- | 5.6 x 1018 | |
| Ag(NH3)2+ | 1.7 x 107 | |
| Ag(S2O3)23- | 2.9 x 1013 | |
| Co(SCN)+ | 100 | |
| Cu(CN)2- | 1.0 x 1016 | |
| Cu(NH3)42+ | 1.0 x 1013 | |
| Fe(SCN)2+ | 900 | |
| HgI42- | 4.2 x 1027 | |
| Zn(NH3)42+ | 2.9 x 109 | |
| Zn(OH)42- | 4.6 x 1017 | |