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 substances is not used as an antacid, we will analyze each option provided.

### Step-by-Step Solution:

1. **Understand the Definition of Antacids**:
- Antacids are basic compounds that neutralize stomach acid (HCl) to relieve symptoms of acidity. They work by increasing the pH level in the stomach.

2. **Evaluate Each Option**:
- **Magnesium Hydroxide (Mg(OH)₂)**:
- This compound is commonly used as an antacid. It helps neutralize stomach acid and is effective in treating acidity and indigestion.
- **Sodium Carbonate (Na₂CO₃)**:
- This compound is highly alkaline. Although it can neutralize acid, it is not used as an antacid due to its potential to cause irritation and burns in the throat and stomach. Therefore, it is not safe for consumption as an antacid.
- **Sodium Bicarbonate (NaHCO₃)**:
- Also known as baking soda, this compound is widely used as an antacid. It effectively neutralizes stomach acid and is safe for consumption.
- **Aluminum Phosphate (AlPO₄)**:
- This compound is also used as an antacid. It works by absorbing excess stomach acid and is utilized in various medicinal applications.

3. **Conclusion**:
- After evaluating all the options, Sodium Carbonate (Na₂CO₃) is identified as the compound that is **not used as an antacid** due to its strong alkaline nature and potential harmful effects.

### Final Answer:
**Sodium Carbonate (Na₂CO₃) is not used as an antacid.**

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