What is observed when testing a sample for carbonate ions with nitric acid?

When a sample containing carbonate ions is tested with nitric acid, carbon dioxide gas is produced as a result of the chemical reaction. This reaction occurs because the nitric acid reacts with the carbonate ions, leading to the release of carbon dioxide, water, and a corresponding salt (in this case, a nitrate). The formation of bubbles is a characteristic sign of gas evolution during this reaction.

Testing for carbonate ions commonly involves looking for the effervescence caused by this released gas, which is a clear indication that the carbonate ions are present. The presence of carbon dioxide can be visually observed as bubbles escaping from the liquid mixture during the reaction.

This behavior distinguishes the correct answer, as a white precipitate would indicate a different reaction involving barium or calcium carbonate, while no visible change would suggest the absence of carbonate ions. Similarly, while carbon dioxide is indeed a colorless gas, the specific mention of “bubbles” in the context of an acid reacting with a solid carbonate is a more suitable observation to note.