The decomposition reaction of Calcium carbonate forms the products as-

When calcium carbonate is heated, it eventually decomposes into products such as calcium oxide and carbon dioxide, which is a significant breakdown reaction followed in many chemical industries.

${\mathrm{CaCO}}_3\left(\mathrm{s}\right)\stackrel{\mathrm{Heat}}{\to }\mathrm{CaO} \left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)$