How does limestone react to weak hydrochloric acid?

Limestone is primarily composed of calcium carbonate (CaCO3), which is a carbonate mineral. When weak hydrochloric acid (HCl) is introduced to limestone, a chemical reaction occurs. The hydrochloric acid reacts with the calcium carbonate, producing carbon dioxide gas, water, and calcium chloride.

This reaction is characterized by the production of bubbles and fizzing, which is the release of carbon dioxide gas. The visible bubbling is a clear indication of the acid reacting with the calcium carbonate present in the limestone. This reaction is fundamental in geological processes and is often used in educational settings to demonstrate acid-carbonate reactions.

The other responses do not accurately describe the interaction between limestone and weak hydrochloric acid: it does not dissolve instantly, it does not remain unaffected, nor does it turn to dust without the acid's action. Therefore, the bubbling and fizzing observed is a direct result of the reaction, confirming that this is the correct answer.