Final answer:
Calcium carbonate (CaCO₃) is a common ingredient in antacids and acts as a base to neutralize stomach acid, often resulting in the relief of heartburn symptoms.
Step-by-step explanation:
The common ingredient in antacids is calcium carbonate (CaCO₃). Antacids are substances that neutralize stomach acid, providing relief from the discomfort of acid reflux or heartburn. When calcium carbonate, which is a base, reacts with stomach acid, which is hydrochloric acid (HCl), it forms calcium chloride (CaCl₂), water (H₂O), and carbon dioxide (CO₂). This reaction not only reduces the acidity in the stomach but also can cause a belch due to the release of CO₂ gas.
Other ingredients found in antacids can include magnesium hydroxide (Mg(OH)₂) and aluminum hydroxide (Al(OH)₃), both of which also act as bases to neutralize stomach acid. However, items such as HCl and KOH are not used in antacids; HCl is an acid and not a neutralizing agent, while KOH is a strong base not suitable for ingestion.