Calcium hydroxide solubility-product constant

Calcium hardness may either be carbonate or noncarbonate. The solubility product constant of CaC03 is K p = [Ca ][C03 ] = 5(10 ) at 25°C. A low value of the K p means that the snbstance has a low solnbility a valne of 5(10 ) is very low. Because of this very low solubility, calcium hardness is removed throngh precipitation of CaCOs. Becanse there are two types of calcinm hardness, there corresponds two general methods of removing it. When calcinm is associated with the bicarbonate ion, the hardness metal ion can be easily removed by providing the hydroxide radical. The of the bicarbonate becomes neutralized by the OH provided forming water and the ion necessary to precipitate calcinm carbonate. The softening reaction is as follows ... 

Some metallic hydroxides such as calcium hydroxide have low solubility and thus are poor sources of OH ions. Note that the solubility product constant, A j.p, for Ca(OH)2 is small, indicating that few hydroxide ions are present in a saturated solution. 

Solubility of calcium hydroxide Dissociation constant of water Solubility product of CaCOa Standard free energies of formation CO, (9)... 

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