The chemical equation for the reaction of CaCl2 and Na2CO3 can be found using stoichiometry; it is written as CaCl2 + Na2CO3 = CaCO3 + 2 NaCl. The equation is balanced using a stoichiometric coefficient, notes Wikipedia.
The stoichiometric coefficient indicates the amount of each compound needed to balance the number of atoms of each element on the left and right sides of the equation. Balanced equations typically use whole numbers only for the stoichiometric coefficient. The stoichiometric coefficient is one for CaCl2, one for Na2CO3, one for CaCO3 and two for NaCl. The two in front of the NaCl indicates two molecules of NaCl produced.