This is a chemical equation that represents a series of reactions involving calcium carbonate (CaCO3) as the starting reactant. The full equation is as follows:

CaCO3 → CaO + CO2
CaO + H2O → Ca(OH)2
Ca(OH)2 + 2HCl → CaCl2 + 2H2O
CaCl2 + 2AgNO3 → Ca(NO3)2 + 2AgCl
Ca(NO3)2 + Na2CO3 → CaCO3 + 2NaNO3

Overall, the reaction starts with calcium carbonate (CaCO3) and results in the formation of calcium carbonate (CaCO3) as the final product.