From the hard water the slaked lime, Ca (OH)2 is used to soften hard water by removing the calcium ions through the following reaction.
Ca (OH)2(aq) +Ca2+(aq) + 2HCO3-(aq) → 2CaCO3(s) + 2 H2O(l)
Although CaCO3 is considered insoluble, some of it does dissolve in the aqueous solutions. Calculate the molar solubility of CaCO3 in water (where Ksp =8.7 x 10-9).