Case Study:

Fourteen-year-old Raghav loved spicy street food. One evening after eating extra spicy noodles and cold drinks at a birthday party, he suddenly felt a burning sensation in his stomach and chest. His mother gave him an antacid tablet, and within a few minutes, the discomfort reduced significantly. Raghav was surprised. “How can such a tiny tablet control the strong acid present inside the stomach?” he wondered.

Before diving into Raghav’s mystery, it helps to refresh your memory on how these substances differ. If you're struggling to tell them apart, check out these simple tips to identify acids, bases, and salts first.

The human stomach normally contains hydrochloric acid (HCl), which helps in digestion. However, overeating spicy food, irregular eating habits, or stress may increase acid production, lowering the pH of the stomach to nearly 1.5. Such highly acidic conditions can cause acidity, irritation, and heartburn. Antacid tablets contain weak bases such as magnesium hydroxide or sodium hydrogen carbonate. These substances react with excess stomach acid through a Neutralisation Reaction, producing salt and water and reducing the acidity level.

A medical intern conducted a simple laboratory test to understand this process. A sample acidic solution with pH₂ was taken to represent stomach acid. After adding a powdered antacid tablet, the pH gradually increased to 5.5 within 3 minutes. The intern observed bubbling during the reaction, indicating the release of gas in some antacids.

This chemical reaction isn't just limited to medicine; you can see similar science in your kitchen! See how lemon juice and baking soda react just like the antacids in Raghav's stomach.

Doctors also warn that taking too many antacid tablets without medical advice may disturb the normal acidic environment required for digestion. Therefore, understanding the pH Scale and controlled neutralisation is important for maintaining digestive health.

CASE - BASED QUESTIONS

 MCQ 

Q1. Why did the antacid tablet reduce Raghav’s stomach discomfort quickly?
A. It increased stomach acid production
B. It neutralised excess hydrochloric acid
C. It stopped digestion completely
D. It converted acid into oxygen

Q2. The increase in pH from 2 to 5.5 after adding the antacid indicates that the solution became:
A. More acidic
B. Neutral
C. Less acidic
D. Strongly basic

 Assertion - Reason 

Q3. Assertion (A): Antacid tablets contain basic substances that reduce stomach acidity.
Reason (R): Bases react with acids in a Neutralisation Reaction to form salt and water.
A. Both A and R are true, and R correctly explains A
B. Both A and R are true, but R does not explain A
C. A is true, but R is false
D. A is false, but R is true

 Application - Based 

Q4. A student says that taking many antacid tablets daily is completely safe because they only remove excess acid. Based on the case study, explain why this statement is incorrect.

Q5. Suppose the stomach acid has a pH of 1.5 and after taking an antacid it reaches pH 4.5. What does this change suggest about the concentration of hydrogen ions in the stomach?

 Data/Logic-Based 

Q6. Observe the data below from the intern’s experiment:

Based on the data, which conclusion is most appropriate?
A. The solution became more acidic with time
B. The antacid gradually neutralised the acid
C. The antacid changed into an acid
D. The reaction stopped after 1 minute

 Application + Reasoning 

Q7. Why do doctors advise patients not to consume antacid tablets excessively even though they provide quick relief from acidity?

ANSWER KEY WITH EXPLANATION

A1. B. It neutralised excess hydrochloric acid
Explanation: Antacids contain bases that react with excess stomach acid through a Neutralisation Reaction. This reduces acidity and relieves heartburn quickly.

A2. C. Less acidic
Explanation: An increase in pH means the concentration of hydrogen ions decreases. Therefore, the solution becomes less acidic.

A3. A. Both A and R are true, and R correctly explains A
Explanation: Bases present in antacids neutralise excess acids in the stomach and form salt and water. Hence, the reason correctly explains the assertion.

A4. Excessive use of antacids may disturb the natural acidic environment of the stomach, which is necessary for digestion and protection from harmful microbes.

A5. The increase in pH from 1.5 to 4.5 shows that the concentration of hydrogen ions decreased significantly. This means the stomach became less acidic.

A6. B. The antacid gradually neutralised the acid
Explanation: The pH value continuously increased with time, showing that the acidic solution was gradually becoming less acidic due to neutralisation.

A7. Excess antacid consumption can reduce stomach acidity too much, affecting proper digestion and disturbing the natural chemical balance of the stomach.

 Mastered this case study?  Take your prep to the next level by practicing these top 10 exam questions on acids and bases to ensure you're ready for any curveball the boards might throw.

HOTS EXTENSION QUESTIONS

Q1. If an antacid makes the stomach environment completely neutral (pH 7), how might it affect digestion? Explain scientifically.

Q2. A pharmaceutical company wants to design an antacid that works quickly but does not disturb digestion too much. What properties should the antacid ideally have?

 Further Practice 
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