A Real World Application of Solubility Products Is Found in Softening

Short Answer

A real world application of solubility products is found in softening "hard water" by removing calcium and magnesium ions present as the sulphate and carbonate salts. We can decrease the amount of Ca²⁺ in solution by addition of sodium carbonate, a strong electrolyte:Na₂CO₃ (s) $\rightarrow$ 2 Na⁺ (aq) + CO₃^2- (aq)By increasing the concentration of carbonate, we tend to drive the solubility equilibrium toward the reactant:CaCO_{3 (s)} Ca²⁺ ₍aq₎ + CO₃^2- (aq) K_sp = 4.7 x 10^-9If the initial [Ca²⁺] = 5.0 x 10^-3 M, what percent of the [Ca²⁺] will be removed if the carbonate concentration is maintained at 1.0 x 10^-3 M?