99. Chemically, what is milk of magnesia?
1. Calcium hydroxide
2. Magnesium carbonate
3. Magnesium hydroxide
4. Sodium bicarbonate

Correct Answer:

3. Magnesium hydroxide

Explanation:

Milk of magnesia is the common name for a suspension of magnesium hydroxide (Mg(OH)₂) in water. It appears as a milky white liquid and is widely used for:

• Neutralizing stomach acid (as an antacid)

• Relieving constipation (as a laxative)

Magnesium hydroxide acts by neutralizing hydrochloric acid (HCl) in the stomach, forming magnesium chloride (MgCl₂) and water, which relieves indigestion and heartburn.

Why the Other Options Are Incorrect:

• Calcium hydroxide (Ca(OH)₂): Also a base, but it’s known as slaked lime, not milk of magnesia.

• Magnesium carbonate (MgCO₃): Sometimes used as an antacid, but it’s a different compound.

• Sodium bicarbonate (NaHCO₃): Also an antacid, commonly known as baking soda, not milk of magnesia.

Conclusion:

Milk of magnesia is magnesium hydroxide, known for its use as an antacid and mild laxative.

Correct Answer: 3. Magnesium hydroxide