Case Study:

Rohan, a Class 10 student, often skipped breakfast and ate spicy snacks during exam preparation. One afternoon, he suddenly felt a burning sensation in his stomach and throat after eating chips and drinking cold coffee. His mother gave him an antacid tablet, and within a few minutes, the burning sensation reduced significantly. Rohan was surprised because he could not see any visible “reaction” taking place inside his stomach.

The doctor later explained that the stomach normally contains hydrochloric acid (HCl), which helps in digestion. However, excess acid can irritate the stomach lining and cause acidity or heartburn. Antacid tablets contain mild bases such as magnesium hydroxide or sodium hydrogen carbonate. These substances react chemically with the excess acid and reduce its harmful effect.

Magnesium hydroxide reacts with hydrochloric acid to form magnesium chloride and water.

Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O

Struggling to get the numbers right? If you find yourself stuck, check out our guide on how to avoid the 5 most common balancing mistakes that even the best students make.

This process is called a neutralisation reaction. Neutralisation is just one piece of the puzzle. You can see how this fits into the bigger picture by exploring other types of chemical reactions explained through real-life examples. because an acid reacts with a base to form salt and water. Even though the reaction cannot be seen directly, it happens rapidly inside the stomach and provides relief. Doctors also advise that too much use of antacids is not healthy, because maintaining the correct acid level in the stomach is important for proper digestion.

CASE BASED QUESTIONS

 MCQ 

Q1. Why did Rohan feel relief after taking the antacid tablet?
(a) The antacid increased stomach acid
(b) The antacid neutralised excess acid
(c) The antacid stopped digestion completely
(d) The antacid cooled the stomach physically

Q2. Which type of substance is commonly present in an antacid?
(a) Acid
(b) Metal
(c) Base
(d) Salt

 Assertion–Reason 

Q3. Assertion (A): Antacids are used to reduce stomach acidity.
Reason (R): Antacids contain bases that react with excess hydrochloric acid in the stomach.
(a) Both A and R are true, and R is the correct explanation of A
(b) Both A and R are true, but R is not the correct explanation of A
(c) A is true, but R is false
(d) A is false, but R is true

 Application-Based 

Q4. A student says that no chemical reaction takes place in the stomach after taking an antacid because there is no colour change or gas formation. Is the student correct? Give a reason.

Q5. Sodium hydrogen carbonate is another substance used in some antacids. Write the balanced chemical equation when it reacts with hydrochloric acid.

NaHCO₃ + HCl → NaCl + H₂O + CO₂

 Data/Logic-Based 

Q6. A doctor recorded the stomach acid level of a patient before and after taking an antacid.
Before antacid – High
5 minutes later – Moderate
15 minutes later – Normal
Based on the data, what can you conclude about the action of the antacid?
(a) It increases acidity slowly
(b) It neutralises excess acid gradually
(c) It completely removes digestive juices
(d) It prevents food digestion permanently

 Application + Reasoning 

Q7. Why do doctors recommend mild bases in antacids instead of strong bases?

ANSWER KEY WITH EXPLANATION

A1. (b) The antacid neutralised excess acid
Explanation: Antacids contain bases that react with excess hydrochloric acid in the stomach. This neutralisation reaction reduces acidity and provides relief.

A2. (c) Base
Explanation: Antacids usually contain mild bases such as magnesium hydroxide. Bases neutralise excess stomach acid.

A3. (a) Both A and R are true, and R is the correct explanation of A
Explanation: Antacids reduce acidity because the bases present in them chemically react with excess hydrochloric acid.

A4. No, the student is not correct.
Explanation: A chemical reaction can occur even without visible changes like colour change or gas formation. Neutralisation takes place inside the stomach and forms salt and water.

A5. NaHCO3 + HCl → NaCl + H2O + CO2
Explanation: Sodium hydrogen carbonate reacts with hydrochloric acid to form sodium chloride, water, and carbon dioxide. The equation is balanced because the number of atoms is equal on both sides.

A6. (b) It neutralises excess acid gradually
Explanation: The acid level decreases from high to normal after taking the antacid, proving that neutralisation occurs over time.

A7. Doctors recommend mild bases because strong bases may damage the stomach lining and disturb normal digestion.
Explanation: Mild bases safely neutralise excess acid without causing harmful effects inside the stomach.

HOTS EXTENSION QUESTIONS

Q1. Why should antacids not be consumed excessively even if they provide quick relief from acidity?

Q2. A chemist accidentally prepares an antacid with a very strong base instead of a mild base. Predict what effect it may have on the stomach and explain your reasoning.

Chemistry isn't just happening in your stomach - it’s happening on your balcony too! To see another fascinating chemical transformation, read about why iron rusts and how it impacts our daily lives.