Question

Why a mild base like magnesium hydroxide is used during indigestion?

• A. To speed up production of hydrochloric acid to speed up digestion.
• B. It neutralizes excess acid in the stomach, relieving pain and irritation.
• C. It prevents the stomach from absorbing nutrients.
• D. It acts as an acid to digest food faster.

Hint:

Antacids must always be mild, non-corrosive bases.
Common antacids include Magnesium Hydroxide [\(Mg(OH)_2\)] and Sodium Bicarbonate [\(NaHCO_3\)].
They temporarily raise stomach pH to relieve hyperacidity.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks for the physiological and chemical reason why magnesium hydroxide (a mild base) is commonly administered as an antacid to treat stomach indigestion.

Step 2: Key Formula or Approach:
Indigestion is caused by the hypersecretion of hydrochloric acid (\(HCl\)) in the stomach. Antacids work on the principle of acid-base neutralization.
The chemical equation for this neutralization is:
\[ Mg(OH)_2\text{(s)} + 2HCl\text{(aq)} \to MgCl_2\text{(aq)} + 2H_2O\text{(l)} \]

Step 3: Detailed Explanation:

• The human stomach naturally secretes hydrochloric acid (\(HCl\)) to create an acidic environment (pH around 1.5 to 3.5) necessary for the activation of digestive enzymes like pepsin.

• During indigestion, overeating, or stress, the stomach may produce an excess amount of this highly concentrated acid.

• This excess acid causes irritation, burning sensation, and localized pain in the delicate inner mucosal lining of the stomach.

• To relieve this discomfort, a mild base like magnesium hydroxide, \(Mg(OH)_2\) (commonly known as Milk of Magnesia), is consumed as an antacid.

• Being a base, magnesium hydroxide reacts with the excess hydrochloric acid in the stomach to produce magnesium chloride (a neutral salt) and water.

• This neutralization reaction reduces the overall acidity of the gastric juices, bringing the pH back to a safe, comfortable level, which immediately relieves pain and irritation.

• A strong base like sodium hydroxide (\(NaOH\)) cannot be used for this purpose because it is highly corrosive and would cause severe chemical burns to the digestive tract.


Step 4: Final Answer:
Magnesium hydroxide is used because it neutralizes excess acid in the stomach, relieving pain and irritation.