IGCSE Chemistry Practice Exam 2026 - Free IGCSE Chemistry Practice Questions and Study Guide

The acid that produces carbon dioxide when reacting with calcium carbonate is hydrochloric acid. When hydrochloric acid (HCl) reacts with calcium carbonate (CaCO3), it results in the formation of calcium chloride (CaCl2), water (H2O), and carbon dioxide (CO2). The reaction can be represented by the following chemical equation:

CaCO3 + 2 HCl → CaCl2 + H2O + CO2↑

This reaction is a classic example of an acid-carbonate reaction, which is characterized by the release of carbon dioxide gas as one of the products.

The other acids listed do not produce carbon dioxide gas when they react with calcium carbonate. Sulfuric acid, nitric acid, and phosphoric acid will react with calcium carbonate, but they do not produce carbon dioxide in the same manner that hydrochloric acid does, or they may produce different products without the evolution of carbon dioxide gas. Thus, hydrochloric acid is uniquely effective in this context for generating carbon dioxide from calcium carbonate.