What product is formed when calcium carbonate decomposes thermally?

When calcium carbonate (CaCO₃) undergoes thermal decomposition, it breaks down into two products: calcium oxide (CaO) and carbon dioxide (CO₂). This reaction can be represented by the balanced chemical equation:

[ \text{CaCO}_3 (s) \rightarrow \text{CaO} (s) + \text{CO}_2 (g) ]

During this process, the heat causes the calcium carbonate to lose carbon dioxide gas while resulting in solid calcium oxide. Therefore, both calcium oxide and carbon dioxide are produced simultaneously.

The other choices do not accurately reflect the products of this decomposition reaction. For example, if only carbon dioxide is considered, it overlooks the formation of calcium oxide. Similarly, if only calcium oxide is claimed, it ignores the release of carbon dioxide. The choice that suggests the production of calcium and carbon dioxide also misrepresents the reaction since elemental calcium is not formed in this decomposition process. Thus, the formation of both calcium oxide and carbon dioxide is the correct outcome of thermal decomposition of calcium carbonate.