What is produced when hydrochloric acid reacts with calcium carbonate?

When hydrochloric acid (HCl) reacts with calcium carbonate (CaCO3), the main products of the reaction are calcium chloride (CaCl2), water (H2O), and carbon dioxide (CO2). The chemical equation for this reaction is:

[ \text{CaCO}_3 (s) + 2 \text{HCl} (aq) \rightarrow \text{CaCl}_2 (aq) + \text{H}_2\text{O} (l) + \text{CO}_2 (g) ]

During the reaction, the calcium carbonate reacts with hydrochloric acid to produce carbon dioxide gas, which is often observed as bubbling or fizzing. This is a distinctive feature of the reaction, indicating the formation of carbon dioxide as one of the products. The presence of carbon dioxide is crucial in identifying the reaction between an acid and a carbonate.

The other potential products mentioned in the other choices do not occur in this reaction. Oxygen and nitrogen are not produced in the interaction between HCl and CaCO3 under normal circumstances. Thus, the primary gaseous product formed in this reaction that is characteristic and observable is indeed carbon dioxide.