Which gas is produced when sulfuric acid reacts with a carbonate?

• A. Carbon dioxide.
• B. Hydrogen.
• C. Oxygen.
• D. Chlorine.

Answer: (A)

When an acid meets a carbonate, carbon dioxide is produced. The carbonate ion reacts with the hydrogen ions from sulfuric acid to form carbon dioxide and water, while the metal from the carbonate pairs with the sulfate to form a salt. For example, sulfuric acid reacting with calcium carbonate gives calcium sulfate, carbon dioxide, and water. The fizzing you see is the carbon dioxide gas escaping. The other gases don’t come from this reaction because hydrogen would only be released if a metal reacted with the acid (not a carbonate), oxygen would require a different decomposition path, and chlorine would come from a chlorine-containing compound, not from carbonate reacting with sulfuric acid.