Why does it become watery white when calcium chloride and sodium carbonate was mixed?

Answer 1

When concentrated aqueous solutions of calcium chloride and sodium carbonate are mixed, the concentrations of carbonate and calcium ions greatly exceed the solubility product constant of calcium carbonate. If the two solutions are mixed quickly, this formation of a solid product occurs almost instantly throughout the mixture, and so many crystals of calcium carbonate are nucleated that each one can not grow beyond colloidal size, because growth soon reaches a point where the ion concentrations are no longer large enough, the ions having been used up to form other crystals. Since the crystals are so small, they remain dispersed in the mixture, turning it milky white, rather than collecting at the bottom of the container as most precipitates do.