Why is calcium carbonate insoluable?

Answer 1

It is a very good question indeed! You see calcium chloride in which calcium is attached to two chlorine atoms is water soluble and vice versa sodium carbonate in which two sodium atoms are attached to one carbonate is soluble. In one to one proportion, calcium chloride molecule is insoluble. Now the answer for this question may go like this. In case of calcium chloride calcium gives one electron to each of chlorine atom. Now both chlorine atoms would have one negative charge. So both of them will repel each other and form the ions of calcium and two chlorine. Thus making them soluble. In case of sodium carbonate, two sodium atoms give electrons to carbonate. Now both sodium ions become positively charged and and would repel each other. So they would form ions along with carbonate. So sodium carbonate has become soluble. Now in case of calcium carbonate, calcium would like to give away 2 electrons but carbon becomes much electrically negative if it takes the electrons. So in this case no repelling force is there to help the metal, it surrenders and form sort of covalent bond and thus ions are not formed. So calcium carbonate is insoluble in water.

Answer 2

Calcium carbonate is insoluble in water due to its strong ionic bonding between calcium and carbonate ions. This makes it difficult for water molecules to break apart these ions and dissolve the compound. The high lattice energy associated with its crystalline structure also contributes to its insolubility in water.