Our stomach produces hydrochloric acid to help in digestion. (a) What happens during indigestion? (b) What type of substances are used as antacids? (c) Why is magnesium hydroxide preferred over sodium hydroxide as an antacid?
Generated by claude-sonnet-4-6 · 2026-06-26 01:04 · grounding rag
Model Answer
(a) During indigestion, the stomach produces excess hydrochloric acid, which causes discomfort, pain, and a burning sensation.
(b) Antacids are mild bases (alkaline substances) that neutralise the excess acid in the stomach. For example, sodium hydrogencarbonate (baking soda) and magnesium hydroxide.
(c) Magnesium hydroxide [Mg(OH)₂] is preferred over sodium hydroxide (NaOH) because NaOH is a strong base and is highly corrosive, which could harm the stomach lining. Mg(OH)₂ is a mild, non-corrosive base and is safe for ingestion.
Source: Chapter 2, Section 2.4.3 (Baking soda)
---
Explanation
- (a) Simply state that excess HCl is produced — this is the root cause of indigestion.
- (b) The keyword is "base/alkaline" — antacids neutralise the acid by a neutralisation reaction (Base + Acid → Salt + Water).
- (c) This is the most important part: the distinction is mild base vs. strong/corrosive base. Examiners expect you to use the word "corrosive" for NaOH. Mg(OH)₂ is mentioned in Activity 2.1 as a base, and the text explains NaHCO₃ is "mild non-corrosive" — apply the same logic to Mg(OH)₂ vs. NaOH.