Which rock exhibits a bubbling reaction when hydrochloric acid is placed on it?

The rock that exhibits a bubbling reaction when hydrochloric acid is placed on it is limestone. This reaction occurs because limestone is primarily composed of calcium carbonate, a compound that reacts with the acid to produce carbon dioxide gas, which is seen as bubbles. Here are the steps of this reaction:

1. Hydrochloric acid (HCl) is applied to the limestone.
2. The acid reacts with the calcium carbonate (CaCO3) in the limestone.
3. This reaction produces calcium chloride (CaCl2), water (H2O), and carbon dioxide (CO2).
4. The carbon dioxide gas is released as bubbles.

This is a common test used by geologists to identify calcium carbonate in rocks.