Which of the following is not used as an antacid ?

Options

A. Magnesium hydroxide
B. Sodium carbonate
C. Sodium bicarbonate
D. Aluminium phosphate

Answer

To determine which of the following compounds is not used as an antacid, we need to analyze the properties and uses of each option provided.

### Step-by-Step Solution:

1. **Understanding Antacids**:
- Antacids are substances that neutralize stomach acidity. They are typically basic compounds that help alleviate symptoms of heartburn, indigestion, and ulcers by raising the pH level in the stomach.

2. **Analyzing Each Option**:
- **Magnesium Hydroxide (Mg(OH)2)**:
- This is commonly used as an antacid. It neutralizes stomach acid effectively and provides relief from acidity.
- **Sodium Carbonate (Na2CO3)**:
- This compound is primarily used as a cleaning agent and is known as washing soda. It is not typically used as an antacid.
- **Sodium Bicarbonate (NaHCO3)**:
- This is a well-known antacid that acts quickly to neutralize stomach acid. It is often used in various antacid formulations.
- **Aluminum Phosphate (AlPO4)**:
- This compound is also used as an antacid. It can coat the stomach lining and provide relief from acidity.

3. **Identifying the Correct Answer**:
- From the analysis, it is clear that Sodium Carbonate (Na2CO3) is not used as an antacid. The other three compounds (Magnesium Hydroxide, Sodium Bicarbonate, and Aluminum Phosphate) are all effective antacids.

4. **Conclusion**:
- Therefore, the correct answer to the question "Which of the following is not used as an antacid?" is **Sodium Carbonate (Na2CO3)**.