Actually, C (carbon) and CO2 (carbon dioxide) are two different compounds. Likewise, H2CO3 (carbonic acid), CaCO3 (calcium carbonate), Ca(HCO3)2 (calcium bicarbonate), CaCO3 (calcium carbonate), and CaO (calcium oxide) are all different compounds as well. They are not directly interchangeable.
Actually, C (carbon) and CO2 (carbon dioxide) are two different compounds. Likewise, H2CO3 (carbonic acid), CaCO3 (calcium carbonate), Ca(HCO3)2 (calcium bicarbonate), CaCO3 (calcium carbonate), and CaO (calcium oxide) are all different compounds as well. They are not directly interchangeable.