Final answer:
Antacids neutralize stomach hydrochloric acid through a neutralization reaction, producing salt and water. The correct equation for the reaction between hydrochloric acid and magnesium hydroxide is 2 HCl + Mg(OH)2 → 2 H2O + MgCl2. Antacids have varying side effects depending on their composition.
Step-by-step explanation:
When antacids are used to treat the discomfort of excess stomach acid, they do so through a neutralization reaction. The hydrochloric acid (HCl) in the stomach is neutralized by an antacid base, for instance, milk of magnesia which is magnesium hydroxide (Mg(OH)2), to ease symptoms like heartburn. The correct balanced chemical equation for this reaction is: 2 HCl(aq) + Mg(OH)2 (aq) → 2 H2O(l) + MgCl2 (aq). Here, water (H2O) and magnesium chloride (MgCl2) are produced, with MgCl2 being the salt formed as a result of this reaction. This reaction is a common instance of anacid-base titration, which can also be used to determine stomach acid concentration.
While antacids like calcium carbonate (CaCO3) also neutralize stomach acid and produce carbon dioxide (CO2), leading to a burp, it's important to note that antacids can have side effects. For example, magnesium-containing antacids can have a laxative effect, whereas aluminum and calcium-based antacids may cause constipation. Some antacids, however, are formulated with both aluminum and magnesium to balance these effects.