FeCO3 is an ionic compound, composed of the Fe(II)2+ ion and the CO32- carbonate ion. Ions tend to dissociate in water, attracted by the partial charges of the molecule. FeCO3 + H2O <---> Fe2+ + CO32- + H2O Water also dissociates into H+ and OH- at a certain equilibrium rate: H2O <---> H+ + OH- Which when combined with an ionic compound is obviously very attractive to the ions in solution... H+ + OH- + Fe2+ + CO32- <----> Fe(OH)2 + H2CO3 Solution FeCO3 is an ionic compound, composed of the Fe(II)2+ ion and the CO32- carbonate ion. Ions tend to dissociate in water, attracted by the partial charges of the molecule. FeCO3 + H2O <---> Fe2+ + CO32- + H2O Water also dissociates into H+ and OH- at a certain equilibrium rate: H2O <---> H+ + OH- Which when combined with an ionic compound is obviously very attractive to the ions in solution... H+ + OH- + Fe2+ + CO32- <----> Fe(OH)2 + H2CO3.